Warning:
When I first switch fire to frost (I lvl'd fire to 55, then made the switch) I was let down. That was not because frost doesn't work well, it was because I didn't know how to use it. I switched back. Then, a few lvls later - I tried it again, stuck with frost until 70.
My advice is to take Frost for 3 or 4 lvls. Promise yourself you'll learn to use it. I didn't understand the idea of slowing the mob, and letting my crits take it out, I didn't understand how the Water Ele is really your FIRST "oh ****" button...
I like it now, I'm what I call "Frost Farming Spec" - which is 100% frost at 70. I'm farming for my mounts. I get the frost, single mob control plus the frost AOE farming benefit. (I'm sure someone here could offer a more efficient spec, but frankly it works. I never die solo, and I can take on mobs in groups easy.)