I myself have not yet reached 70, but I'm taking time to get some gear in Azeroth so I can level a little more effectively past 45. That, and I'm dealing with professions.

I would suggest the 5 Moonkin druids - that's my main group and it only gets better every day. Instances can be a little tough, but cloth all of a sudden rocked when I got to 40.

Hopefully, you can reach 70 by the time wrath comes out so you can start fresh with whatever group you choose to keep up.