I've been reading quite a few reviews of Serenity and the word is mostly positive. Sadly though, one of the reviews from here is in Empire Magazine. I have to say that it's possibly the most wishy-washy review I've read in that mag for quite a long time. It compares Serenity to other sci-fi films and talks about the B-grade cast, but does very litle commenting on the actual film.
A very well written review can be found at Your Movies, an Australian movie site. Sign up for the weekly newsletter and on Wednesday, September 21, you will be able to see the Serenity review, trailer, synopsis and an interview with Joss Whedon.