I am pretty mixed on this unit after playing with them in a few tournaments. They just don't seem to perform as well as my unit of Fiends of Slaanesh. On one hand they are more survivable against shooting, but they just don't seem to live as long. My Fiends are able to hop from battle to battle because they are so fast, and when they hit anything less than a Land Raider it usually goes away.
The Bloodcrushers also cost about 50 points more than my units of Fiends that I run.
As awesome as these guys are I think I am going to shelve them for a while and model up some more Fiends and see how they treat me.