I built this spec for pvp in 3.1 http://www.wowhead.com/?talent#jcEzo...ofziost:cThM0m. I'm waiting for some comments about it, and maybe improvements. I also would like if you post your pvp spec. I looked around but haven't find and pvp specs thread.
With the changes to Death Strike, having some survivability is key. Either take some points in Anti-Magic Shell and Anti-Magic Zone and follow up with a Glyph of Anti-Magic Shell, or go throw some points in blood and get rune tap or something.
I'm using an unholy PvP build that is Unholy/Frost. Just enough points in Frost for Endless Winter, the rest are in Unholy. Up to you I guess what you want to do.