To people not in the know, the actual physical sensor size (in mm^2) is many many times larger than say the iPhone 4S and at least twice as large as many standalone compact cameras . The biggest sensor before this in any cameraphone has been in the N8 (to my knowledge) and this one has an even bigger sensor.

So its not just the megapixels, it is backed up an actually physically large sensor. Add in the great Xenon flash (which gives out much larger amount of light than say the tiny LED flash on the 4S) and you get a great cameraphone.