Shipping April 5, $800 price tag just for the headset so youll need to have previously purchased a Vive or pick up your own base station(s) and controllers.
I snap-preordered because a) the graphics are supposedly much improved b) Unity3d suddenly supports legit AI agents c) fuck yeah Elite Dangerous with maybe great graphics and d) Amazon Prime = regret insurance.
Other interesting points; the cable is thinner, they redesigned the light-blocking flap thing, and it has integrated headphones apparently.
Relevant stats:
2880x1600 (615ppi) = 37% ppi increase and a 78% overall pixel count increase.