I think the movie muddies things a bit from what the series did but, overall, caps off the universe as a whole nicely, though more movies would've been nice.
I can say that seeing Serenity twice in pre-release screenings was some of the best theater-experiences I've ever had.
Funny thing to note, in the "blooper real" for the movie there's a scene of Nathan Fillion ad-libing as Mal as they prepare to leave Book's planet. He instructs the crew to but Book "right up front, he's our friend we should honor him!" Funny scene to watch as you can see some members of the cast giggling, most notably Jewel.
I think the movie muddied a couple aspects of the series. For example at no
point in the series does Simon demonstrate that he has the suave and ability to pull off the "Academy" heist we see him pull-off in the opening scene of the movie. The "idea" behind the Reavers seems to have changed some, in the series they seem more mysterious and analogous to how some settlers precieved the Native Americans. Simply as "savages." But "savages" who're also able to operate ships and organize battles, etc. In the movie they're more like Hollywood zombies/monsters.
Really a lot of the stuff dealing with River and how much Simon "knew" seems pulled out of nowhere but there's likely a season's worth of development missing there.
Your "injury" report for the movie didn't include how every member of the crew suffers injury during the course of the movie. Mal gets beaten up pretty badly by The Operative, Zoe gets her back slashed open by the Reavers, I believe Jayne gets shot by the Reavers, Wash gets impaled by debris/projectile weaponry from the Reaver ship, Kaylee gets shot by the Reavers, Simon get stabbed/shot by the Reavers. Infact, I think the only ones to come out of the Reaver battle untouced are Inara and River.
And as much as it sucked to have Book die, Wash dying was even worse. But as much as I hated it I agree with the overall belief there was at the time that killing him made the final battle that much more tense. Because if Wash can be killed out-of-the-blue like that then no one
is safe as, again, everyone takes some pretty hefty injury during the final scenes.
And I wasn't a big fan of Mr. Universe either. I think it would've made a bit more sense to use Badger as an "inside man" or even Patience to help the crew get their goals. It seemed out of place to introduce this guy out of nowhere.
The movie is good, mostly does what it set out to do, but I in the end it makes me long more for what could've been.