Serenity was a bit of a disappointment. Admittedly, I was never one of those "brownshirt" types - if for no other reason, than I'm not into fascist self-identifications. Whedon *had* to have known the provenance of "[x]shirts", right? It's basic political literacy. But all that aside, I did like Firefly, enough to buy the DVD set and watch 'em a couple of times.
Firefly was a fun, small show - an extended family of rogues and no-better-than-they-ought-to-bes bumping around the edges of a harsh and largely uncaring universe. I liked that about the TV series - that there was a bigger world out there that gave nary a damn about our heroes. The world didn't revolve around them, and that was a good thing. They were, after all, crooks. Whedon was quite explicit about this thematic element of the show - that it was an existentialist universe, and that any meaning was made by the characters.
Serenity, on the other hand, is decidedly *not* an existentialist film. At least, I can't see that in it. There's a clash between the conservative rebel protagonists, and the idealistic, zealous authorities. Said authorities, which could be characterized in the TV series as a vast, numb, heedless beast, oppressively large and unloving but not particularly swift or clever, became in the movie a smallish conspiracy of savage, nanny-state conspirators and true believers. I could see where Whedon was going with the Darkness at Noon, 1984 line of attack, but it isn't really a theme that *works* in an action piece. For one thing, it's a much more Burkean/Russell Kirk/early neo-conservative sort of attack than what he was pushing with the TV series. It's very much the sort of thing that I associate with P.J. O'Rourke and his hostility towards government and idealism of any sort.
I really have some cognitive dissonance issues with a tireless-Kerry-campaigner like Whedon writing a film like this. I strongly suspect that I've misunderstood the line of argument, but I can't help but see what I see: idealists' best intentions destroy anything they touch, and they must be fought in the name of the imperfectability of man. The Mal of Serenity *is* WFB's conservative standing athwart history, shouting "Stop!"
The movie has other issues, such as the discard of much of the series' atmosphere and humor for the Logan's-Run-by-way-of-Frank-Gehry bits on Miranda and the big space battle bits and the Reaver butcheries. I think it wouldn't have felt so much out of place as a big two-hour, two-episode show-piece within a full Whedonesque season of context, although that would have presumed a great deal of re-writing, I suppose. But as a stand-alone, it was fairly bleak and lacking in what I found charming about the Firefly concept.
Both Fillon and Whedon have complained about the way the network made them lighten up Fillon's Mal, and have indicated that the original conception was more bleak and Serenity-like. If this was the idea, I think I'm with the suits. Mal is harsh and more than a little unlikable, once you remove those grace notes of black humor and buffoonery.