I leveled from 1-70 as Holy, I do very much to see all the content I can, but I made a decision to be the First Priest to 80 on my server. So I'll be questing nonstop as Shadow, then once that is out of the way, I'll take my time on my Prot Warrior or my Rogue.
I was considering leveling Smite for awhile, but after giving Shadow a try I think it would faster that way.