To be honest, there's not a lot of "learning" required -- I was able to pick up the new shadow priest pretty easily. You have to refresh SW:P now, but that just takes the spot on your keybind that Devouring Plague did. Sure, you have to fire off your Shadowy Apparitions when you hit 3 orbs (or sooner, if you're moving), but they feel more important and satisfying now that you can control when they happen. VE moves onto your toolbar to replace Divine Hymn as your powerful emergency heal that you don't have to stop DPSing to use.

All classes are going to get new abilities and lose old ones -- it's just part of the new expansion process. Give the shadow priest a try before you say you're hanging up your DoTs for good. It's a work in progress, and really, it's not that bad.

To be fair, this iteration of the MoP shadow priest is streets ahead of the one from a few months back. A lot of the changes seem scary, like losing the always-on VE. In the long run, though, I think that change is an improvement (as is the press-to-cast SA change).