Since they brought up arcane above, I'll add that I leveled frost, though now that I'm 80, both mages are arcane spec'd. I've been finishing up quests in Icecrown for gold and AB+Abarr+Wand(for the last 250-500 health) in my mediocre gear flattens mobs quite quickly. Plus, with the short short CD of Evocation, mana effeceincy is no longer an issue. I did, however, stay away from missile barrage because it provides no benefit to a boxer unless it procs on all your mages. Arcane is great for PvP, good for dungeons/raids, and decent enough in solo questing (I'd still prefer frost solo).