After greedily watching the best part of Firefly in a weekend, I became slightly obsessed and got increasingly frustrated that, having missed the run of Serenity in UK, it was later than advertised in Florence, ran only for a week I had to return to Liverpool on a Thursday. (And it was just that bit out of town that I didn't manage to get to it.)
Now though I did finally see it, and was slightly disappointed. I understand recapping the Tams/crew tensions that were resolved in the Objects in space for the benefit of first-timers. I also get that myth-rewriting can justify airbrushing out the men with hands of blue (too sillysinister and powerful?), but I was irked that Simon here knows more about River's situation right at the beginning than he discovered only in Ariel and later in the series.
But that's nit-picking, just like my "oh, look, Mal is now inexplicably able to defeat the far superior bad guy in hand to hand combat, yawn" concern: more importantly, the grand secret at the heart of it was unconvincing, especially the reactions (personal and political) to it. And a general point that there could be many more secrets was glossed over.
Hrmpf, I guess that's also nitpicking, I guess I just didn't get the same sense of fun, adventure from this as from the series.