I think he is great... the emotion that the dragon shows in CGI is awesome, so much so that you still feel so much emotion towards Eustace, even when he can't speak or anything like that. also, the colour matched the sort of colour scheme that VDT came with if you see what I mean? and i can see some resembalences between Will and Dragon Eustace (No offense ment!)
My only problem is how the bracelet ends up being so huge when Lucy removes it, but so small originally!? But this is move of an error and really not much to do with actual dragon, but as I was writing, i thought I might mention it anyway

I think he was only really weird in the poster shots of him. He looked nice in the film.

He definitely didn't look as terrifying as I had imagined him from the book, especially with the Pauline Baynes illustration. That one would have to be my favorite illustration out of all of them. He looked a bit too friendly for me.