So, basically, what everyone is trying to say is:
Wraiths move 12" in movement, and 6" in assualt. They can only move 6" in the assualt if an enemy unit is in range of their charge.
And, personally, I think Wraith are a good addition to an army, but only a large one, say 1500pts+. They are good for taking out Fast Attack units that are trying to flank you, or if anyone gets too close.
While I'm on the topic of Wraiths, does anyone else feel that they should have at least one attack that is Armour Peircing? Terminators are, what, 35pts? And they have 2 armour peircing attacks, even if they do strike last.
Isn't the Shock Whip good for anything these days??