Last night I switched from Elemental to Resto and tried to do some daily quests. After about an hour of that I was thoroughly dissatisfied and decided to log off. I felt I couldn't do well in PVP as an enhancement and PVP is definitely necessary on my PVP server but yet enhance is fun to solo with. Resto is great for instancing because you can still pop off lightning spams when on easy fights, but it totally sucks for doing quests... horribly sucks. Last is Elemental Spec which I hadn't done since level 30 or so when I switched to Enhancement.
I didn't run instances, but I jumped into a few battlegrounds and was very happy with the results. Even with 1/2 my gear still being enhancement and the other 1/2 lower level 70 crap I have been saving just in case I needed to respec, I completely modified any situation I encountered.
Come up against a large group fight and I would just pop off some heals to the team mates to get us even and then LB and Earth/Frost Shock to cancel out the enemies life. I loved to death doing the 2 sec lightning bolt critting, getting a 60% less mana shock spell and using the 3 min cool down for a guaranteed crit. Plate drop to 1/2 life and clothies drop to the ground.
I have always done a ton of damage in Enhancement, easily able to pull aggro from prot warriors, but that isn't necessarily a good thing. I wanted a spec that would allow me to help out the group for instancing, wouldn't take forver to solo with, and allow me to back-up heal and occasionally main heal for the easier 70 instances. Elemental/Resto seems to fill that roll very well.
As a quick side note, once we finished the Battleground (AV) I checked the Damage meters and I noticed at the top it wasn't a mage, lock, hunter, rogue, or DPS warrior, it was a Shaman. I checked him out in the Armory and he was elemental. Now not only was he/she the highest, but he/she was at 215k damage while the next person (mage) was at 160k. Something to grind your gears on... :)