Excellent overview by Brian Klug for Anandtech.
This aside about sensor pixels is amazing:
The current generation of modern pixels is around 1.1 microns square, basically any 13 MP smartphone is shipping 1.1 microns, like the Optimus G, and interestingly enough others are using 1.1 microns at 8 MP to drive thinner modules, like the thinner Optimus G option or Nexus 4. The previous generation of 8 MP sensors were using 1.4 micron pixels, and before that at 5 MP we were talking 1.65 or 1.75 micron pixels. Those are pretty tiny pixels, and if you stop and think about a wave of very red light at around 700nm, we’re talking about 1.5 waves with 1.1 micron pixels, around 2 waves at 1.4 microns, and so forth. There’s really not much smaller you can go, it doesn’t make sense to go smaller than one wave.
Smartphone pixel density is hitting a wall because the light waves are larger than the pixels.