This new Protoss unit is very powerfull and strategic in SC 2 Beta. Especially if your opponent is Zerg and making fast Zerglings and he is going to advance Roach technology, Void Ray counter attack will be wise. Fast Void Ray tactic can be imagined like fast Corsair tactic in Broodwar, the basement of these tactics are almost same. But Void Ray is more expensive but it can attack both ground and air and its anti building bonus is good. You can destroy enemy Command Center or Hatchery in the early periods of the game easily, then you can advance Carrier/Mothership technology without problem but remember that Stalker feed must be constant during this technological advance.