Spriest mastered it, to fly under the nerf radar completely. There is even a dev quote to it.
This is the most fun and strongest spec availble at the moment.
Of course i wonder what happens in 5.2 with those new monks, as blizz gave them possibly op tools(ring of peace) just to drag them into pvp more.
BTW, my favs are Unholy DK, Warlock(any spec), Mutilate Rogue, Fire Mages and Disc/Spriest. And since i played very long all of them were my mains at one time. Currently having fun with uh again(but, they better bring 5.2 changes soon, as the mechanisms are the most clunky ones in the entire game!) and especially feral druid/rdruid. I personally prefere specs that stack up a ton of debuffs on your target.
---------- Post added 2013-01-23 at 05:28 AM ----------
Learn to use macros, especially pet macros, they are required for uh to play at all, it certainly nothing for beginners, also writing own macros helps greatly too.