I re-specced my fire mage to frost last week and I'm pretty bored with it already. Both DPS and survivorbility is pretty low.
MW
I started out as fire, switched to arcane when I found how low fireball hits for (2k) and after trying arcane did the inevitable switch to frost, which I've always hated but have tolerated for levelling. However it's so far behind the DK I've lost heart. The DK could literally smash down 7-8 mobs AT ONCE with cooldowns in dps spec. The Mage can't kill two without lots of tedious micromanagement. This micromanagement used to be fun when you were doing something other classes couldn't do, but now it's just extra effort and you still can't keep up.
I boosted the Mage from 81 to 90 (yeah yeah I wanted to play it there and then) but now it seems like a waste.