I saw Angels & Demons last week, and I really enjoyed it actually. Coming from someone who read the book years ago, it has tweaked and changed a few bits, bit it still retains the main plotline and feel of the story, and it all works well. The bloke who plays Commander Olivetti is scarily like I pictured him when I was reading the book! The one big change, of changing an italian character to an irish one, and then getting a scotsman to play him (which is a move that makes you think "why not just get a decent italian actor?") actually works quite well, and gives a bit of extra padding to the story, where Dan Brown can regularly be found focusing on facts and realism, and every now and then forgetting a bit about back stories.
8/10.