Instead they come up with a nice twist on the expected "zombie" origin story that we've come to expect, and while I won't ruin it for you if you've not caught wind of it yet, I will say it's a clever mixing of horror sub-genres. The mystery aspect helps the goings on feel a lot more fresh than they might otherwise play.
It's also always fun to see highly trained operatives face a situation like this, as opposed to the usual "normal people". It ups the ante effectively, and in the case of REC 2, gives multiple camera angles to pull from since all of the SWAT members have helmet cams. Unfortunately that makes it all the more painful when the middle block of the film dumps the SWAT angle for what feels like forever to focus on three idiotic teens. One character in the trio is so annoying I nearly fast forwarded through the section. Pure padding, and that is the films Achilles hell.
Before long though, we are thrust back into the creepy thrill ride and we get a very satisfying ending that ties well back into the original. It's not quite enough to overcome a critically flawed second act, but it does avoid letting that flaw turn fatal.
Audio: Spanish Dolby Digital 5.1; English and English SDH subtitles
Behind-the-Scenes documentary: One of the best of these I've seen
A Walkthrough of the Set featurette
Sitges Film Festival Press Conference featurette
On Tour featurette