Holy **** Spriest is the most fun I've had on a class in AGES.
ETA: Here's a basic rundown of the Spriest:
You have the standard Spriest rotation, but now you generate Insanity. When you reach 100 Insanity, you can enter Void Form. Void Form ups your damage and unlocks extra abilities, but drains your Insanity at a gradually increasing rate. For each second you spend in Void Form, you gain a stacking Haste buff that persists after Void Form ends, and until the buff either expires or you next enter Void Form. Essentially, Void Form is a short period of high streaks. Your goal is to stay in Void Form for as long as possible, and you achieve this by GOING ****ING HAM. The better you perform, the longer you stay in Void Form, and the more benefits you get. That's the gist of it. (Also, Void Form looks ****ing gnarly.)
For me, that period of high streaks is so ****ing good. You enter Void Form, you play this little mini-game, and when you leave Void Form you get to see how well you did, represented by your Haste stacks. Did you get 30 stacks? 35? 38? 40? Each time you enter Void Form it's like a competition to out-do the last one, and it's so inexplicably fun. Your rotation doesn't feel like a rotation, it doesn't feel like a chore, it feels like a mini-game. For the first time in a long time, I'm not watching CDs and timers, I'm having fun.