Adapted from a response to friend's negative review of Serenity:
I saw it last night with a large group of rabid fans. They even brought extra Jayne hats, so they could lend some to those without.
I didn't think it was that bad. I liked it quite a bit, actually. I've never seen any of the series, but it had what I'd expect from a Whedon production: intelligently aware (not in the psychological sense, but in lack of blindness to audience-transparent plot elements) characters, some clever dialog, characters (though not necessarily villains) with realistic values systems, conflict between personal goals/needs and obligations to others, and zombies.
He thought the fighting was dull. I gave the fighting a pass. It was no Crouching Tiger, but it was fine for a grittier feel, and they did a good job individuating the fighting styles of the characters. It also didn't give me epilepsy from cut times that last 0.7 seconds on average.
The characters were almost all caricatures, though not sterotypical ones, but I got the feeling that they had some depth to them that would come out with more time, so I wasn't nearly as unhappy with it as you were. Generally, there's not time to develop that many characters in a single movie anyway.
I didn't agree that the movie took the typical hackneyed "artifical/technological attempt to improve humanity goes horribly awry" philosophy. I thought the movie was making a more social/political point than a philosophical one. It vilified the Alliance for testing the drug in secret on such a wide scale, then escaping accountability for its actions. The villains were the parliament, and the scientists were tragic. I thought the zombie subplot was kind of a fun, and he tied it into the main plot at the end. I guess I just didn't have my realistic science fiction hat on.
In general, I thought it was a good, enjoyable movie. I will likely borrow the DVDs and watch the series. It isn't the "godsend of modern filmmaking," but it's a damn sight more entertaining than the majority of dreck that hollywood is putting out: I dare anyone to say with a straight face that Deuce Bigelow 2 was better than Serenity.