Tried it out yesterday. Really a major improvement, and they're listening to feedback. The method of producing 'low persistence' is quite interesting, and only works becuase of the move to OLED. Really smart guys there.
Carmack has been talking about OLED for VR headsets for quite some time, and I'm sure Palmer and the rest were considering it, too. But I think it wasn't very accessible to them until recently. They're a start-up so they can't exactly go an order a few thousand 1080p OLED panels. This may have been possible now due to Samsung making the Galaxy S4 with a 1080p panel last year, and perhaps other launched some, too, and it pushed the prices down for such a panel, enough to make it viable for Oculus Rift.
They have over $90 Million in venture funding. They can order pretty much anything they want.