I leveled from 62 to 70 full Resto, and I loved it. Instances weren't hard to get into for sure, and survivability is pretty sweet. You may move a bit slower than enhancement, but if you like healing (I'm weird, I know), then Resto is the spec for you.
Also, there are many quest rewards you need to get in these levels that aren't bad for pre-heroic gear...ex. Totem of the Plains from the Mastery quests in Nagrand. You'll use that until the xpac every time you cast LHW for sure.
EDIT: Of course, you could still pick these up while leveling enhancement. One route is to level enhance but pick up any +healing quest rewards and instance loot.
Edited, Nov 10th 2007 10:59am by GWynand