It's a good movie - exciting, funny and scary. The characters and dialogue are just as interesting as the (very good) special effects for a change, which is something we haven't really seen in a sci-fi blockbuster since Star Wars ep 4-6.
The basic plot is not disimilar to a Buffy or Angel season finale (the gang must unite to defeat a big bad against the odRAB - here represented by a mean sword-wielding Brit) but it really kicks into gear in the final third and trancenRAB its TV roots. Sort of a cross between Star Wars, the Dawn of Dead remake and, in places, Kill Bill.