I can't think of anything bad to say about this series, aside from wishing that there was more, and that the River backstory could have unfolded in due time instead of all at once. I'd also like to see Inara naked (my GF even thinks she's hot). Hell, River too - she has that Fifth Element weirdo ninja quality about her to make up for whatever making up they did to have her look screwed up. Great character - she's Wolverine, Dr. Xavier, Snake Eyes, Carrie, John Nash, Robocop, and Tetsuo rolled into one.
They paid homage to so many great series' of the past that I don't know where to begin, the dialogue was very good, and the acting was good enough that I was sucked into watching the entire thing over 2 days while working at the same time.