The only real problem with MistWeaver is that you are doing the same thing a Resto Shaman does... just worse. If you are evenly geared in Super Intelligence gear (which you should be)... as a MW you are attacking up close and you in more danger all the time, and your heals are pretty much similar. You can heal more as a MW, but not by much, but the damage is WAY in Resto's favor... and its ranged damage so you are less likely to just me killed.
I do like both, but... resto just has the true power here.