Their pretty neat. Granted its only one game, and not nearly all the units, but looking at what he did play with, THeir fairly balanced. His list and some thoughts:
4 dire avenger squads
2 swooping hawk ones
1 maxed harliquin squad
avatar
wraithlord with bright lance
1500pts.
Why anyone would take guardian squads over dire avengers is beyond me. DA have a nice balace of offense and defense when built right. Bladestorm is nice.
Harlquins are a glass hammer. You literally live or die on a '6' roll of the ide. Yeah, I watched them buzzsaw through a unit of marines, but they couldnt kill through a terminator cammand squad, got bogged down, then counter charged by two scout squads and it was over for them. Yeah, I only had the chaplin left out 6, but he lost all the harliquins. Fair trade.
Avatar pretty much is a blood thrister w/o wings. But his key problem is: he moves 6" a turn. You can deal with him like you would a wraithlord: ignore it and manuever around it. I forced him to slog length wise down the board to come to me, while fighting other parts of his army.
Eldar book is nice, what I've seen. Cant wait to face more.