KK, so I hit 70 earlier this week (...wait for applause...) and I've stuck with Enhance spec. Gotta say I'm loving it. Upon hitting honored with Shat, Cenarian and HH I've been able to pick up a few very nice blue pieces and dropped in some gems.
In BG I'm having a blast. Run into the main battle grouping, target nearest, frostshock and purge. Dropping a few totems about as well (windfury, SoE). I'm not doing the greatest damage but my dps is still pretty kickin.
In raids I've found I'm making quite a bit of a difference. The use of the (what the hell's it called...brain fart..anyways) Fear supression totem has saved the party from some nasty situations and the windfury totem is cracking up some nice dps for the rest of the raid. The Ancestral Spirit rez is quite handy. I'm also running a bit of off healing and support/defence of the primary healer when needed.
And yes, in World PvP 1on1 I'm getting my *** handed to me quite often, but, it's expected and accepted.
With PvP and BGs I'm aware that I'm a SUPPORT class. I'm not an 'off-tank' or a secondary healer. I know that with a few odd off-heals, well placed (and appropriate) totems and a respectable amount of dps, an enhance shammy can be quite an asset if the class is played well and if the player understands and accepts their class limitations.
If your enhance and thinking that at 70 you'll be a tank (or even an off-healer), it just ain't gonna happen - but it's loads of fun if you accept it for what it is.