As you know Arbiter is rarely used in multiplayer games because of its high cost and high technological need,but it is becoming popular in multiplayer games especially against Terran or Protoss.Arbiter has very high potential dependent of its cloak ability and recall.The recall ability really changes the destiny of the game.For instance if your opponent has a very well defended entrance,the Arbiters will play very important role during your general strike.You can directly by pass the enemy defenses and harm the production locations(factories or gateways)But here the important thing is the seperation of your army ofcourse.Because if you seperate without strategy the both of your forces(with Arbiter and independent from Arbiter(s)) can be eridicated by the enemy.So you must set the seperation very carefully so you will have an efficient result may be you will have victory by only this movement.Arbiters are nice.