[doogless]

Frost isn't really the tanking tree, or at least not since they redesigned them. They spread tanking talents across all 3 trees, although a lot of people spec into Frost for Howling Blast (very good for multi-mob threat), Lichborne (good for an extra avoidance boost), and Unbreakable Armor (good for an extra mitigation boost). There's also some DKs who prefer Unholy for tanking because of Bone Shield, but there's no single "tank" tree like for Paladins or Warriors. Currently their threat is pretty amazing, but they have some problems with the "not dying" part of tanking. I did Halls of Stone (level 77 instance) with a DK tank, and the only issue seemed to be that some bosses just plain hit him too hard, and he was wearing the full blue crafted tank set (so it's not like his gear was lacking).

DK DPS is pretty insane right now, specifically Dancing Rune Weapon. It ends up being a 100% DPS increase when it's out, and if you have 100 RP when you activitate it and use it every cooldown, it ends up being out about 30% of the time. 30% damage increase for 1 talent point is pretty amazing, but it was mentioned by Ghostcrawler that it's going to get toned down.

DKs in PvP hit really hard, and Death Grip is really annoying! You'll be minding your own business, nuking people from range and then BAM you're in the middle of 5 angry horde.