Taking this from a different angle, I found myself wondering what the target age of the movie was halfway through it. The jokes seemed awfully pubescent. A little low for me? But I see people than me enjoying this movie. Or am I born of a generation jaded by these things (I'm in the 18-24 category)? Or is it the elusive age category that I'm in?
I've seen a few episodes of Buffy previously, and noted its typically lacking television dialogue. What disappointed me was that the construction of Serenity's dialogue did not much improve over what I've previously seen of Whedon's work. But this I can forgive -- the movie is obviously meant to be taken as light. Dialogue that sounds hopeless unrealistic doesn't matter.
Two things really bothered me though -- both typical of Whedon, imho. The first was the presence of a female do-it-all. She's attractive, she's innocent, and she kicks much more ass than a girl of 100 pounds can viably kick. It's a little cliche. I was hoping could do something more original of his own work.
The second, which bothered me even more, was the presence of a completely unnecessary romance. It's 2006. Thus, unless your target audience is 12-15, you do not need a romantic side plot. Imho, if you are to include such a plot, you have to give it more weight. Does it sell the movie? Sure. Is it sh*tty? Definately. But writing things into the plot to make more money does not earn my respect.
Now, on to things that were good. Whatever budget this movie recieved was probably enough to buy some serious digital editing capabilities. Some of the space shots were amazing. I guess I'm a sucker for well done CGI.
And of course, the transitioning was good. Take the first scene -- I was truly impressed with the pacing. Keep the audience in one mindset long enough to do what you need to do (first the setting was introduced, then 2 major characters), but before we're comfortable, we're thrust out, onto something new. Clever as hell.
All in all, I give it a 70, which, in my scale, is a heavily flawed, predictable, but enjoyable flick.