Ok,
Great Story, Great effects and Joss does his usual character developement (if you were fans of Buffy and/or Angel you get my drift).
Reading the 3 comics that came out just before the movie will help you fans of the show understand what has happened since the last episode. If you didn't watch the tv show (what is wrong with you), I think you can still pick up on most of what is going on.
Lots of plot lines get tied up so that is nice but one of the organizers said he spoke with a Universal rep who told him if the movie makes at least $80Million, they guarantee 2 more sequels.
As for the "freakshow", not sure where you have been but the "freeks" are the ones to thank for this movie hitting the theater. I have not seen so much fan and fan-atic support for a cancelled show ever. The organizers are filming a documentary named "Done the Impossible" that deals with how the fans are responsible for getting the cast back together and continuing the story. My son and I ended up first in line so we may even get in the doc. Now, I didn't wear a browncoat but a few did and there were several "Companions" in the audience. 13 people participated in the costume contest (no lightsabre battles in the line), there was a raffle for several film related items, we saw clips of the shows and tidbits of info (poll on who is the sexist lady in the crew, Kaylee won by the way), etc keep the crowd entertained until the witching hour struck and the ship hit atmo as they say.
Already see one potential dio idea in 35th scale and wish someone would make the ship as a kit.
Bottom line... Go see the movie. Several times.