I dropped it for Shadow Power recently too, and in raiding its not a really large loss. Usually my VE doesn't get to top my group off, due to Chain Heal or an overanxious Paladin, so all I'm doing is topping my group off a bit slower. On fights with a lot of AoE I also notice my threat is a bit safer. The worst thing about it with raiding is it takes longer to top yourself off after a SW

now, and usually a healer will waste a heal on you because you're topping yourself off slower and they don't realize you're doing it to yourself.
The place you miss it most is definately PVP and grinding, but its worth the 2 talent points in Shadow Power IMO if you're a pure raid spec.