I figured this could use a separate topic to the Spaced one.
Saw it yesterday. Absolutely smurfing brilliant. A lot of critics are saying it isn't as good as Shaun of the Dead (comparison is unavoidable, I guess) but I think it is definitely equal to it, if not better.
It started off pretty slowly, but once it got going I fell in love with it. It's definitely the best police/action move/TV Show parody I've seen. Simon Pegg and Nick Frost are very clever men.
I don't need to comment on how good the humour of it is, although a fair chunk of it is very British, and I think it will be lost on American audiences, but I'm sure they'll still find a lot of the movie funny. The action scenes, though, are awesome too. (SPOILER)Granny drop kick and (SPOILER)gun carnage in a small village, featuring a crazed battle in Somerfield's? Priceless.
If you're British and you haven't seen it, go see it. If you're not, wait until it comes out in your country. Then go see it.