Mages bring more to the table than just food and water

They have crowd control, can lock packs down with frost nova, slow targets movement, and in frost can even have a permanent pet, not to mention insane DPS. That's just the tip of the iceberg really. Each spec opens up new avenues.

I'm finishing off my old mage to throw into my group just to have a fall back in case Cataclysm is unfriendly to non-mixed teams. They're fairly powerful and definetly a fun change if you've just been playing 1-2 classes for ages.

You also have a TON of time man before Cataclysm. Time enough to level several characters to 80 without much effort if you spread it out over time. Like my mage I just play him when he has rested exp and it doesn't seem like such a chore.