Ry saw it prerelease and so did Kevin.  James and I went to the first showing in the area and got back about an hour ago.  It was very good.  James had a few nits to pick but I shot down most of those.  I had one nit to pick and James shot it down.  As expected with anything that Joss Whedon helps write is going to have some great dialog.  This was no exception.  Jayne, as usual, is so incredibly self centered and delivers his lines with such timing and such a straight face that the audience bursts into laughter.  I think my favorite was when someone (trying to avoid spoiling it for someone) says:

Someone: "Do you really think any of us are going to get out of this alive?"
Jayne (looks around, pauses): "I might."

My favorite lines of the movie were the following (as best I can remember):

Someone 1: "If I had known this was going to happen I would have done things differently.  Back on the ship I would have been with you."
Someone 2: "Are you saying... sex?"
Someone 1: "That's what I'm saying."
Someone 2: "To hell with dying.  I'm going to live."

In another sequence:

Someone 1: "Landing could be interesting."
Someone 2: "Define interesting."
Someone 1: "Oh god, oh god, we're all gonna die?"

This is a "Space Western".  It's a good one.  Lots of guns and blades and a good message.  And as Kevin said in his review:

Go see Serenity. You won't be disappointed if you like this blog.