I'm not a huge Twilight fan but I thought that the movies have been pretty enjoyable, particularly the last one (which I thought was the best). This first part of BD was a lot of setup (presumably for the next part) and dragged along until Bella discovered she was pregnant and things got tense between the wolves and the Cullens, as well as between Jacob and Edward.
The first part of the movie- starting with Bella's pregnancy- reminded me a little of the Vampire pregnancy storyline from S3 of Angel- there being a mystical Vampire pregnancy that the pregnant character is struggling to take to term because of incompatible physiology and there are a lot of outside players trying to destroy it, take it, or figure out how it happened. I suspect that the second part will probably be more enjoyable/entertaining now that the buildup to the birth has been addressed and Bella's outcome has been....ahem.....determined. I loved the abrupt ending but it was a bit jarring to go from such a serious ending to bouncy alt rock music for the credits.
I haven't read the book so I don't know exactly if they needed two movies to get everything crucial in it but, like with the last HP movie, I was so engaged in the movie by the end that I really think that, given a brief intermission, I could've been able to sit through another 2 hours and finish it- though I understand that having both parts together would make it commercially difficult for movie theaters. I can't believe that we have to wait a whole freakin' year to see the conclusion. *ugh*