I like the fact that Wash died, and I thought it happened at a great time.
When I went to see the movie with my girlfriend (it was my second time and her first) she was as nervous as hell during the fight with the Reavers. When Zoey got cut, she was genuinely afraid that Zoey was going to die. When Kaylee got shot with the darts, she was genuinely afraid that Kaylee would die. Same with when Simon got shot. Same with when River got stuck outside with the Reavers.
Wash's death had a purpose; it showed you that Joss took off his kiddy gloves. If Wash didn't die when he did, then we'd just assume that there was no real danger of any of the other characters dying because... well, because they're the "good guys."
I still think it was one of the greatest movies I've ever seen. I just don't get what so many people have problems with.