When I saw the stats on the Shadow Specters, I ordered three squads of them right then and there in the Battle Bunker. They are my heavy unit of choice for all three slots.
Other than not being used in most tourney lists, it seems alot of folks I talk to are not happy with them or don't find them worth filling a heavy slot. I am not sure why, so I thought I would throw myself to the (Fenris) wolves and see what others had to say.
Greg