I think the green mist is just a way some nightmares express themselves, after all they aren't trying to defeat the mist but the darkness itself.
The mist is only shown 3 or 4 times, 1 going down the stairs on the DT, 2 as the WW over Caspian's bed, 3 going among the men on the ship and 4 as the WW to Edmund.
But all the rest about it just shows it as darkness, which would correspond with the book.
The long and short is I think it is just expanding darkness that makes nightmares come real, isn't that scary enough and it is based on the book.

So maybe the DI sends out the green mist.

Once again, I found myself voting "Other" ~ not because I feel torn among the many options here, but because I'm thinking of one that isn't mentioned here. That is the rumored scene where Aslan allows Reepicheep into His country because it is "made for noble hearts," and Reepicheep is noble-hearted. I'm not denying that Reepicheep is noble, for noble he most certainly is, but that is not the reason he gets to go to Aslan's country. Keeping that line in the movie would completely contradict the idea of salvation by grace so clearly demonstrated in Eustace's un-dragoning. That's if the un-dragoning is done right, which is my second-greatest worry and the option I would choose if I didn't have the choice to vote "Other." To me, the other matters are all secondary to those two. (And I'm actually quite excited to see Peter and Susan.)

I've resigned myself to most of these changes, but I'm still worried about the undragoning . Most of the other problems we already know more or less how those will turn out, but there is still confusion and conflicting spoilers surrounding that scene. I'm still upset about the other stuff, but I wouldn't say I'm worried about them anymore than I'd say I'm worried about Suspian.

I voted other because at this point I think the only thing I am worried about is Lucy's character. Only because we don't have enough information to determine how extensive this "I wish I looked like Susan" story is going to be. It could just be a few lines here and there or it could be annoyingly overdone. I don't like it, but if its only a few lines I can roll my eyes and move on. But if she's insecure and unsure of herself throughout the film, it just wouldn't be Lucy.

I don't like the seven swords plot and the way they completely replaced the events at Narrowhaven, but I've resigned myself to it.

The Ed/Caspian/ Lil thing looks like its just a cheesy line for laughs (I hope) and it looks like Ed and Caspian are friends through most of the movie with the exception of the arguement at Goldwater. Big sigh of relief.

We have recieved confirmation (can't remember where--maybe that interview with Mark Johnson that was removed?) that the White Witch will only appear in Edmund's nightmare. I thought maybe that's why they removed that interview. They have hyped up the White Witch's role so much that they don't want anyone telling the fans that she's only in the movie for a few minutes.

I am a little worried about the undragoning because Eustace's journey is, for me. the most important part of Dawn Treader. My favorite part anyway. I really hope they get it right.