I haven't read any of the Twilight books, so I went into this movie without expectations. I thought it was beautifully shot with beautiful actors. (There's plenty of eye candy for all to admire.) There was a certain campiness to the film that I appreciated; it didn't take itself too seriously.
The audience was full of excited (vocal) Twilight fans, which made the experience even more fun. (I've always enjoyed going to big movies on opening weekend. There's a certain energy in the air.)
As far as vampire movies go, Twlight doesn't have the depth of an Anne Rice adaptation or the action of an Underworld or Blade. (To its credit, it doesn't seem to need those things to work well and feel fresh in a genre that's been done to death.)