My druid is pretty well set for gear and such so I have been spending increasingly more time on my alts. Sure the essence of gossamer still hasn't dropped for me so I run AN every chance I get, but other than that all my upgrades will come from raiding which I do 8.5 hours a week (seems a lot when you look at it).
So my two up and coming alts are a resto shaman and a rogue; there is also my good old hunter which was my first 70 and main for a while. It is looking like my shaman will be the next to hit 80. I am waiting for the hunter class to settle down a bit before I work on my hunter again, didn't fancy respeccing and pulling aggro off my pet with autoshot using aspect of the viper got old fast. My rogue is mainly a disenchanter for my own convenience as well as a tailor to make bags, so my goal it to just keep it leveled to the point where I can max my professions.
My resto shammy, Shiksa, has been resto since level 1, even though my first talents weren't till level 10 and I think I stuck my first few talents in enhancement anyway. Still aside from a few points in the enhancement tree for some flavor I am full resto. Back in the day my hunter was my DPS, my druid was my tank and this was to be my healer. Things changed, feral dps became viable and dual specs are looming on the horizon. Come 3.1 my druid will be a jack of all trades, literally. So that left my alts without purpose aside from me becoming more self sufficient with added professions and eventually having a second 80 to raid with (goodness knows one is not enough). I did enjoy running with two guild 10 mans back in BC.
I also have a death knight over on the horde side which I play with from time to time. My realm is pretty alliance heavy so the horde side is a little sad. My guild has a horde alt guild which runs 5-man content once or twice a month. I have been meaning to look into other guilds I may get more out of, but it is a lower priority since my work on the alliance side takes the majority of my time still.
So as far as leveling with a resto specced shaman goes, I like it. I get a good grasp on healing keeping myself and those around me from dying which keeps the skills sharp and lets me tweak my hot keys over a long period of time. I may not be able to kill things very quickly, but they can't kill me at all so there is a trade off. And actually when I get really crazy and pull 4 or 5 yellow mobs and a 6th and 7th comes along I think I dps pretty well comparatively since my magma totem scales very well with more mobs. Water shield keeps me topped off mana wise to lay in with chain lightening between heals. All in all a very interesting and different way to go about leveling. Now for a priest or druid I would not see resto as a very good leveling spec, but I have very little experience with priests.