I'm looking forward to it. But, I wonder what the ideal challenge mode comp will look like...here's my guess:
(Obviously there's some wiggle room since 3+ classes can provide the same buff, but ideally on challenge modes you're probably wanting something that can provide sustained burst/little to no ramp up time)
Prot Warrior (For speed runs, I've always found warriors to be ideal. When played well, to me, they're amazingly beautiful. A DK is a close second)
Holy Paladin (This one is hard - they can't heal on the run as well as a disc priest or druid can, and since most 5-mans are clumped, shamans tend to do well too. But, hpallies heals hit hard and with proper use of holy power, you can spam out impressive healing - single target and "aoe" - Anyway, we'll see)
Mage (arcane or fire, depending on which spec is FotM) BL and burst dmg - sure shamans can provide BL too, but there's better alternatives
Spriest (I feel up in the air about this one but I like spriests more than moonkins so meh)
Rogue (maybe a DK) mainly for AS% but obvious burst/sustained high dps as well (more so rogue)
Feel free to share your ideal comp, thoughts on Challenge Mode, etc.