I went to see The Watchman on Friday, choosing a cinema trip, over the requisite night spent drinking in the LES. Because I read the book, I appreciated the book's close adherence to the text, I also thought they improved the ending and made it more believable, emphasizing the similarity between the work and 9/11 (though it was written well before the tragedy.)
It went on a bit too long though--the movie started at 11:50 and ended at 3:00 am, people kept getting up and leaving the theater. I nearly fell asleep but I made it until the very end. The changed ending seemed to have a great similarity to the Dark Knight flick.