As I understand it, this is purely a raid dps spec, meaning:
* It's got mana issues in 5-man heroics where you don't have mp5 buffs from other classes. I would assume you will need to drink a lot in heroics, and some bosses might even be much harder. Personally I find that Thunderstorm mana "cashback" is a life saver on long boss fights.
* It's crap for pvp.