So far I've run then out in three games (one against Necrons and two against Blood Angels) and they've rocked (largely due to their being joined by Belial)). They certainly add something to the list, they can't be ignored and they seem to be able to stand up to an almighty amount of unfriendly attention.
Next up, it's back to the Greenwing. The Command Squad is almost done, just the Banner of Devastation to paint (yikes!).