Daybreakers is a vampire District 9. Maybe it's not quite as profound, mind-blowing or game-changing, but it does have an obvious social metaphor and it's good fun. In this vampire world, they've pretty much used up all the humans, so they're starving for blood. While scientists try to find a blood substitute, one vampire (Ethan Hawke) discovers there is a cure to turn them human again.
So obviously what they're really saying is that vampires use up their resources and end up just like people do. Then there's the business of manufacturing a product to replace natural necessities. Finally, there is the underlying truth that even with a "True Blood" or a cure, some people will just want to be vampires drinking the real thing.
The first part of the movie sets up the world, and it's a cool place you just want to live in. It explains the shift in the balance between humans and vampires, and just how vampires live as a majority. Their cars are rigged with video feeds (since they can't use mirrors), and their underground tunnel system is cool. It's obvious, with vampire Uncle Sam banners in the background, but at least it's visual. It's not characters telling us, "This is why this happened, and this is why we have to do this." They have some fun with it, too, if you pick up the background comment about vampires causing forest fires.
It's kind of cool that they used the traditional vampire mythology and played with it. They don't cast reflections, they do burn in the sunlight. It's not some newfangled diamond skin or fangless wonder. They just adapt to the practical concerns. God, it's nice to see real vampires again. Forget Team Edward and Team Jacob. Join Team Ethan!
Once they establish the rules, the film kicks into high action mode. A car chase in blacked-out cars is awesome, and you feel the stakes of losing the video feed or bullet holes letting in beams of sunlight. These are problems Vin Diesel and Paul Walker don't have in their car chases. Vampire attacks are fast and powerful.
It's B-grade enough to be down and dirty, but with an A-list cast and production value. Well, at least a B+ production value. It's bad CGI, but so is everything that Peter Jackson or James Cameron don't do. What happens when vampire medicine goes bad, or when vampires mutate, is nasty.
The tone of the film is serious and somber, because being a vampire is not fun. Just surviving is getting tough for them. Everyone talks in a gravelly rumble. That might be the effect of vampirism, or just really intense acting. There's a good father/daughter issue, too. Kids, you may rebel against your parents' rules or curfew, but at least they're not vampires who'd condemn you to immortality.
The cure feels right in the mythology, too. I wonder why it took someone 200 years to think of that.
The one glaring question is: Why wouldn't they just keep humans breeding to produce more? I'm sure if you put humans in co-ed camps, they'd end up doing it. You could even bribe them with treats if they produced more offspring. Hunting them down and hooking them up to a draining grid seems overcomplicated and less well thought out.