The Night Spinner rules are out via the latest White Dwarf. Here's what the Eldar are getting:
Night Spinner
72" S:6 AP: - Large Blast, Barrage, Rending, Twin-Linked, too!
Any units hit moves as in difficult and dangerous terrain during their next turn.
BS:3
12/12/10 Fast, Skimmer, Tank
Linked Shuriken Catapult
Standard Eldar vehicle upgrades apply.
NOT a transport.
Costs the same as a Fire Prism
This looks a LOT better than just a S6 AP - template like it was first rumored to be. The rending will sort of make up for the AP - and the difficult/dangerous modifier is really nice. We are starting to see more powers that work this way - Murderous Hurricane from the Space Wolves is one - so I bet we will continue to see more of it. My money is on Dark Eldar having a lot of powers and weapons like this.