Or all the way up till 70

Personally I dont know why everyone assumes that leveling as a healer spec is so difficult, I have 2 healers at 80(pally and shaman) both I leveled as healers, its not any more difficult than leveling in a DPS role, it just takes as little longer, but if you know your calss right, things actually go much faster. Once, in borean tundra, to win a bet, I gathered up as many rhinos as I could on my pally in holy spec, threw down consecrate, threw up ret aura, and spammed heals on myself, killed over 20 in that first pull, took less than a minute.

Annother advantage to leveling in a healer spec is that when in dungeons, you can learn to use your abilites as the sutuation calls for, for example: if the tank pulled too many, and lost aggro on a few, its a perfect time to cast chain heal to heal up those overachieving DPS. Or if the tank is clearly a decently geared tank, knows what he is doing, then you can relax and use mana efficent spells to keep him alive, and to heal DPS that take a hit or two, and overall make the instance go faster because of fewer mana breaks. Frequently in lvl 80 heroics, I am just spamming one spell(chain heal for shammy, flash of light for healadin) and using it to keep everyone alive, frequently not caring if I am overhealing beacuse I have so much mana(32k on pally, 24k on shammy with over 600 MP5). at lower levels, where your gear isnt as good, your stats are MUCH lower, you need to quickly learn how to manage your spells and resources, and at low levels is the best time to do it, because the odds are, if you fail in a lvl 80 heroic, ppl will RageQuit or try to kick you, but in leveling dungeons, you DO have some leeway, a wipe in BRD wont destroy the group(but getting BRD frequently might make ppl quit anyway, ALOT of ppl hate it, but I love it) and because BRD can have some ... Tricky pulls for a newer group of players, it the perfect place to experiemnt(Within reason, no stupid junk tho!!) and learn your class.

BRD probably wasnt the best example, it was just the first to jump to mind, but Gnomeregan is a good example, SM Catherdral, and even DM can have some tricky areas to pull in(think that hairpin turn just before goblin foundry).

Oooo... that's a great point! My understanding has been that up until the 40's or even 50's you didn't REALLY have to specialize in healing (just be a healing class) to be able to get your team through an instance. Of course, maybe that's from the old days... now you've got a nifty dungeon finder, and you play with people who have 10 alts and full sets of heirlooms... not how it was when many of us were leveling our first. Maybe our expectations are higher now in what we expect from group healz while leveling?