If they're anything like the old DH2 and DH3 (which they are, just with more travel) then they are awesome. Plushest fork I've ever ridden. However, they are pretty flexy. They don't like hitting rocks at an angle on off camber sections, tend to make a fairly horrible noise as they bend round it... Damping is amazing though, so well worth the dough. You can pick up the old DH3's (with the piggyback) for peanuts though, and they are just the same but with 7" travel.
not like old dh2/3 (which i agree are amazing and prob best fork ive ever felt, just, as mentioned flexy/finiky). lots of stiction, and poor dampening (as said by pinkbike and a shop buddy who bought one...and regrets it)