I have a general dislike of Facebook which has kept me away from their headsets, however this actually seems like a great idea.
Wearing a computer on your face instead of on your back has been one of the most asinine design choices of standalone vr. Comfort issues from putting weight on your neck while you're expected to look around, the headset jostling around because of the momentum of the weight, the heat buildup from having both the screen and the computation on your face. Trying to solve these hurdles by making the computer itself more lightweight and cool has probably had other tradeoffs, likely regarding performance.