Was sold out at the Odeon on Wednesday, which put paid to my fears of it totally flopping over here as well as in the US, although the downside was that I couldn't see it. Hopefully I'll catch it on Tuesday, already wiki'd it to see how the ending differs (script was written about the same time as the final book) and it seems worthy of holding my nerd-rage in check. Certainly better than the total cop out that was Kick Ass (or the unmitigated mess that was Wanted).
I went to three different screenings on Wednesday and Thursday and they were all sold out, summer holidays I guess...
As for the differences, the film follows the book almost panel for panel until the Todd Ingram battle, it looks like they used the comic as the storyboards for most of it. After that it really is quite different without sacrificing the overall story and themes. I found a number of changes turned out a bit better than the book, the Katayanagi twins battle is much better, and using the Battle of the Bands thing as a through line for the whole movie is a great decision, it makes a lot of sense and means the other characters have a reason to stay with Scott for the whole thing.
I did miss Knives' dad, Honest Ed's and it could have done with more Envy Adams though.