My shammie was 100% elemental until she hit lvl 60. Between her gear and crits she was virtually unstoppable. Sadly, however, on my server nobody wants a DPS shammie. We pull way too much threat apparently. So I respec'd to Resto. I have discovered she is still amazingly overpowered. With earthshield she gains life when she is hit, so you drop that with stoneskin and then grace of air, you're feeling pretty darn good hehe. Not to mention Mana Tide totem is a Godsend. I get invited on more raids now since I respec'd because everyone wants a resto shammie because of our buffs and healing. I have yet to try out the enhancement tree....was thinking about creating a new toon to give it a shot. Had a friend who was 100% enhancement and that girl was a tank..i.e she could take some MAJOR blows.
Good Luck!!!
~Arna