Went to watch HP7, P1, too, yesterday.
Spoilers!
I must admit that the last time I read the book is some time ago, so I wasn´t completely up-to-date, but still the movie was easy to follow, since most of the important things were in it, and also pretty much how I imagined them. Sure, there were some minor differences from the book, like Harry not taking Polyjuice at the wedding, and some things were cut short, like the trio planing their infiltration of the Ministry, but these things aren´t that bad.
The images were quite dark and powerfull. I really loved the animated story of the Three Brothers and the scene were Ron destroyed the Horkrux. So the movie was really good in capturing the books dark atmosphere. I really can´t wait to see the 2nd Part with the epic "fight" between Harry and Voldemort.
IMO this movie was one of the best and closest to the book. Mainly because it was seperated it into 2 parts.
Definately a 8.5/10