I enjoyed this movie (4 out of 5 stars), but it's been a little while since I read the book, so I've probably forgotten the parts that were removed. That is a big plot point that Umbridge sent the Dementors, as it makes her even more complicit in the Ministry discrediting Harry.
I rank this film 3rd behind Azkhaban and the Goblet of Fire, mainly because it felt rushed. Yes, it's still longer than two hours, but it needed time to relax, and another 10-15 minutes would have made it even better. We could have had more with Sirius (which would have made his death more powerful), and the end would have felt clearer. Still, I enjoyed the movie as a whole.
To someone who read the books recently, is Bellatrix more involved in the book? I remember her playing a larger role, but she's barely present here. The scene of her leaving the prison is effective, but her role seems diminished (until the end.)