I'm not sure why, but I started in Hyjal, then switched to Vash'jir. I don't really like the 3-D-ness (I see the turn-in question mark! is it up or down???) of it, but I kept going there, then switched to Deepholm. But it was slow going there under 83, so I went back to Vash'jir until the last (I hope) set of quests bugged out, then back to Hyjal. I want to finish up all the Hyjal quests tonite for the rep, then back to Deepholm. I like the way the quests in Deepholm are laid out because you can do more bunches than in Hyjal/Vash, but I hear that it's -even- better in Uldum. In other words, I've been pretty ADD about leveling. :)
Archaeology is kind of fun, but very slow. Rested xp is amazing, though. (PS don't turn in your fragments till you get past lvl 75!!!)