Meh. I enjoyed it. At least it tried something different. I've never thought of sparkle vampires, or other things that Meyer created in her realm. Granted, Bella and Edward annoy me, but the other characters (especially Carlisle and Esme and the family members close to Edawrd) were enjoyable and pretty unique. The other three books are much more compelling (with the exception I suppose of Breaking Dawn, which is pretty much on the same level as Twilight).
I think what most people hate about Twilight is that it turned Vampires into something other than horrible creatures of the night. Well, that's at least what my classmates tell me anyway. I think it also received a fair amount of criticism because of it's "emo" Romeo and Juliet-like nature, and most people hate "emo" kids (or people that try to emulate them), and anything they like is automatically disliked.
Then again, I might just be totally wrong, really naive and have really poor standards when it comes to literature and film. (which is probably the case, although I don't put this in my top lists anywhere, and have better works far far ahead of them).