Wash's death was tragic and painful. Book's death was, well, kinda pointless. Bad enough you don't give the guy a real part in the movie, but man, then you gotta get him killed? Feh. (Side note: Wash and Book were my favorite crew members.) Whedon's portrayed it as a tough universe before, I understand the theory, but man. (Having all of Wash's dinosaurs up on the console at the end was a nice touch.)
As noted elsewhere, I don't know why they retconned River's escape from the facility. All it really does is make Simon a slightly less believable character.
As for the film itself, pretty enjoyable stuff. Some... interesting lighting decisions, which I'm gonna have to let sit with me before I make final decisions on that. Fine and dandy jump cuts in there, though. And a number of other Whedon trademarks.
More later, and in comments in other people's stuff.
Side note: I'm very interested to hear reviews from regular people who saw the movie *without* having seen the show.