Other upcoming competition, which should be released this week is the BluBur S1:
The headset doesn't have 4k but does have a 1440p panel, which at least is a bit higher than the Oculus and Rift. The really cool thing about it though is that it has 120 hz ! This should stop the motion sickness (which I do experience with the Pimax)
It also comes with controllers !
Oh and it's Display Port 1.2, so it actually CAN support the max settings (unlike Pimax). DisplayPort 1.2 does support 1440p @ 120 hz, even without compression !
Gearbest says it's shipping it out next week: http://www.gearbest.com/pc-headset/pp_423477.html?wid=21 I think I might buy one and see how it compares to the PIMAX
*EDIT * it seems the Gearbest offer doesn't include the controllers. I'll wait till at least the controllers are also available.
EDIT2 I'm also not sure if Gearbest is really shipping out next week, weird thing is that on their website they don't show anything regarding a release this week, so who knows ... I'll wait for more info, but this seems at least something interesting