I'm lucky I had the chance to play with DK1. It was amazing experience, a breakthrough technology that worth a lot more than 2B in the long run.
IMHO oculus rift is doomed from now. Even if a scenario where Oculus remain a completely independent entity (i.e. FB sees nothing from this investment), Oculus already lost a lot of its community, especially those who dont like facebook (http://www.ign.com/articles/2014/03/25/notch-minecraft-on-oculus-canceled-facebook-creeps-me-out)