Frank's fate seems uncertain, but I suspect he also died, since he was knocked unconscious in the sinking sub.

I thought that we were going to lose Kate when she got shot (seemingly to the heart), but in reality it was much worse!

I'm afraid I really don't understand Sayid. They made this big deal about him being evil, then he got to play John's aloof and emotionless handmaid all season until finally having mercy on them all and sacrificing himself. Huh, what?

What does, "It's going to be you" mean? It really seems like Jack is the new Jacob. I wonder if they've made it too obvious and will switch it at the end.

Why aren't Kate and Hurley candidates? Are Jack and Sawyer the only remaining candidates?

I cried over the Kwons' deaths. Sun is my favorite female on the show, so I'm very sorry to have lost her. It was nice to see how much the Losties cared about them though... Jack was pretty distraught.

When do we get to see Richard and Ben again?

I do not understand why Flocke wants them all dead. That's just the rule? In order for Smokey to leave the island, Jacob and all candidates for his replacement must be dead. That seems weird.

In the alternate reality, a plane crash caused John's paralysis and his formerly-healthy father's vegetative state (though unintentionally) - and it seems John is denying himself healing due to guilt or penance.

And Jack is trying to help John because he's a candidate, while on the island Jack is trying to stop Locke because he's a candidate.

Island - Our Lostie friends are taken by Widmore's crew to our beloved polar bear cages. No matter what people think of the cage episodes, you have to agree that the Hydra Station is pretty awesome. The cages are surrounded by numerous transportable sonic pylons to keep Smokey at bay. But they don't have the generator up and running just yet. We discover Widmore has a list with the candidates names (Jacob's list?)

LA X - Jack wishes to help Locke by performing surgery, so he decides to stick his nose into Locke's business. He visits his doctor, Bernard Nadler. Awesome! It's great to see Bernard actually practising his profession. Granted Jack was being a bit nosey, but Bernard still came off a bit creepy in his Oracle (Matrix) like state-of-being.

Island - The MIB is royally peeved that the other Losties have abandoned him (although I'm pretty sure he realised that they'd do it at some point - he's not stupid). He tells Jack that he could kill them all, but he won't, he wishes to save them from Widmore. Doc Jensen in his Entertainment Weekly column (Totally LOST) suggests that the MIB can kill the candidates himself, but that if he does so, it violates the rules of the Island and prevents him from ever leaving. On the other hand, if he indirectly gets them to kill each other, that's another story. I quite like this theory and it seems perfectly reasonable at this stage.

Sawyer tells Kate that her name was on the wall (it was about time the show addressed that cinematography mishap) but that it was crossed out and she's no longer a candidate. I wonder if this means that she will become a variable, a wild-card of sorts. Still, I hope it's Desmond. He's a more compelling character but then again, we want him to be reunited with Penny and little Charlie.
Sun and Jin have a lovely little moment in the cages, involving Jin's wedding ring and talk of their daughter Ji Yeon. Beautiful and heart-warming. It certainly makes up for the underwhelming reunion last week (maybe it was planned that way - phase 2 of the reunion).

The power goes out, Stormy roars through the base and kills several guards. He looks amazing in this scene (almost his old self). There's a deadly but graceful quality to his movements, something similar to how I imagine a Chinese dragon might glide through the air.
Frank has a hero moment as he tries to kick down the door, but this isn't a Burt Reynolds movie. Jack appears and rescues them all. He tells them that he's with 'Locke'. They go to meet up with him.

LA X - Jack continues to be nosy and visits Anthony Cooper, who is in a catatonic state following an accident. Jack discovers Cooper is Locke's dad. Cooper was a real mongrel but here I almost feel sorry for the man. Almost.

Island - The MIB takes on Widmore's guards, surrounding the Ajira plane. He removes a watch from one of them and pockets it. ? The MIB climbs inside and finds something hidden in one of the compartments. What is it? The Losties arrive at the Ajira, joyful to be almost of the Island, but no such luck. The MIB emerges from the plane and convinces them that Widmore was trying to blow up the plane with them aboard; then he produces a slab of C4 explosives from his backpack to seal the deal. The MIB makes new plans, for them to all make for the submarine, so they can leave the Island. Sawyer's had this plan for awhile. He's been conning the MIB and gets Jack in on his plan. He wants Jack to push the MIB into the water, so in the confusion, they can escape via the submarine.

LA X - Asleep in his hospital bed, Locke mumbles about pushing a button and wishing Jack had believed him. These are two obvious references to events that happened in the Island reality. They're really bleeding together now! Claire meets up with Jack and they talk about their father. It's a great moment for the two of them.

Island - The Losties make it to the shore where the submarine is but they lie low, so they're not shot by Widmore's crew. The coast is presumably clear, so some of the Losties climb aboard the submarine and take control. The others follow suit and the MIB stays long enough to make a switcheroo with his and Jack's identical backpacks (I didn't notice it the first time, so what happens next was even stranger). Jack talks to the MIB, as they make for the submarine pier. The MIB pleads with Jack to leave the Island with them but Jack won't have any of it. The MIB tells Jack that whoever told him that, was stupid. Jack replies that it was John Locke and pushes the MIB into the water. All hell breaks loose and Widmore's guards ambush the pier. They shoot Kate - dead? Wow. No, not quite. Kate's never been a favourite of mine but I've never hated her. It must've taken some guts for the writer's to harm her. The rest of the Losties manage to make it to the submarine and it dives beneath the waters as a distraught Claire watches on.

Below the surface, Jack searches for some clothes to stop Kate's bleeding. He digs into the backpack and finds - explosives! The C4 comes complete with a watch (so that's why the MIB needed the watch). The bomb counts down the minutes and seconds, Jack and the others watch in horror. They try to surface but there's not enough time! Jack comes to the realisation that the MIB long conned them all and that they'd fallen into his mousetrap. Jack believes that the MIB can't kill them, just that he wants them to kill each other. Some aren't convinced, especially Sawyer. It's a really tense moment. Here we have two rivals facing each other off in a life and death situation. It's like the hatch button situation in Season 2, with Jack and Locke, only inverted and deadlier (sort of). Jack believes that nothing will happen if they leave the bomb as is - he's a man of faith now. Sawyer is still the sceptic and believes they should pull the wires to stop the bomb. Sawyer pulls the wires and the timer counts down even more quickly! Oh no! Pulling the wires out doesn't slow and then stop the bomb, but activates it!

Being a military man, Sayid tells them that there's nothing for it, but that there's a well on the Island, with Desmond in it and they have to rescue him. He suggests that Jack is the candidate!, picks up the bomb and dashes away. He runs for all he's worth but the explosives detonate, Sayid is killed and chaos reigns. Great moment! Zombie Sayid has been redeemed and saved others. I liked Sayid for the first few seasons but later didn't. This moment justified his character for me. Very sad. Frank Lapidus follows suite, when he's killed by a flying submarine door as the water fills the submarine.

Sun is trapped beneath some wreckage and Jin comes to her rescue, so do the others but they can't remove it and they're running out of time. Tough decisions follow. Hurley takes an injured Kate to the surface and Jin convinces Jack to take an injured and unconscious Sawyer and leave them. Jack grabs the only remaining oxygen tank and leaves with Sawyer in tow. Sun and Jin remain.

Jin still can't free Sun, so he decides to stay with her, so they can die together. Beautiful, tragic, heartbreaking. Some fans have said that Jin is a selfish mongrel for not trying to swim to safety, so Ji Yeon has at least one parent, but think about it. There are no more oxygen tanks on the submarine and they're going down fast. Water is filling the cabins and time is running out. Even if he wished to escape, he wouldn't make it alive. Better to live his last few moments with his wife, than die alone. Live together, die alone. I was shaking throughout the sub-explosion and aftermath scenes (probably came from trying to hold in my emotions). I did get a bit teary though. Sun and Jin were never my favourite characters (although I enjoyed them quite a bit) but, like Sayid, they were with us from day one. I grew to love them as a married couple and watching their journey unravel. The (almost) last two seasons have relegated their importance to minor characters, which was saddening but inevitable. I wish they'd been treated better but at least their send-off as truly amazing.

LA X - Upon leaving the hospital, Locke encounters Jack and bypasses Jin on the way (yay! but how are they going to make us care for our favourite Losties on the Island, if they're still alive in the sideways reality? Please don't let it be an epilogue. Please let that reality be manufactured by Smokey. Jack tells Locke that he went to find his dad. Locke isn't pleased about this but finally reveals that he had a pilot's licence for one week and took his dad flying with him. They had a terrible crash, with terrible consequences. Jack tells Locke to let go of his guilt and pain. Locke replies that he doesn't find it easy. Jack confesses that he'd hoped Locke would help lead the way. Jack wants to help him regain his ability to walk, but Locke will have nothing to do with it. He leaves.

Island - If we didn't cry enough already, we do now. Hurley, Kate, Jack and Sawyer make it to the surface. They mourn their friend's deaths. It's absolutely heartbreaking, especially when Hurley began to weep. Jack walks into the waves and screams into the night.
Meanwhile, the MIB senses that the submarine has sunk and killed the Losties (but probably not all of them?). He retrieves Claire and they head back into the jungle - to finish what was started.

Epic.

Where they are now:
I can't remember where Ben, Miles and Richard are at the moment. I think I remember something about going to the Dharma Barracks to find explosives to destroy the Ajira plane. I don't think this is the last we've seen of them. It's certainly possible that Richard and Miles will be killed by Smokey and that Ben will rejoin the Losties.
Both Widmore and Smokey will hunt down the Losties.
Hurley, Kate and Jack will likely mourn their friend's deaths a while longer, then Sawyer will join in when he awakens. They will question everything. When they've collected themselves, they'll probably make for the well, rescue Desmond and then he'll give them A New Hope.

I think the explanation that the MIB cannot leave the island until the candidates are dead - and that he can't kill them but can manipulate them into killing each other - is valid.