MORE SERENITY REVIEWS: Here, here, here (“Where Sith was fast food that left you feeling nothing but gas, Serenity was a seven course meal.”)
Also here, here, and here, as well as here, here, here, and here.
UPDATE: Here’s another, from Will Collier.
ANOTHER UPDATE: Neil Gaiman and Joss Whedon talk about stuff, in Time.
MORE: Still more blog reviews, here, here (“Much better than anything Lucas has done in the last 10 years. Go see it.”), here, and here.