I haven't leveled ONLY in rested xp, but damn near. Since my girl and I play the team together (I 3box and she plays her priest) I've kept it to only playing when she can, of course her limited schedule and my raiding schedule on my main kept that to once a weekend, sometimes twice...

My goal each week was to grind through as many quests as we could AND blow all our rested xp each week... most weeks we did it!

As we level towards 70 I'll get a lot more playing on my own done, but it wont be for leveling, it will be for farming gold... my plan is to farm LBS from the old world dungeons as they sell for 150G/stack of 20, and considering how absurdly easy I blew through warlords command at 60th I see 4 boxing the old world instances being complete ezmode by 62... I dinged 61 on the paladin only (she's about 50% of a level ahead) and replaced all my old world gear with stuff that would make your average MC gear equiped pally cry.

Not that MC gears all that great anymore, but considering the rings I replaced were from level 20 and 35....