Messed around with a few specs on target dummies on PTR last night. Most of them feel pretty simple at 100 without artifacts, but that isn't necessarily a bad thing.
Demo lock is fun, but unless I'm playing it wrong (very likely!) soul shard generation seems a lot faster than spending. Hand of Gul'Dan and summon Dreadstalkers are pretty much all you need to spend them on, and one of those has a 15 second CD. I was using a few talents that made Soul shard generation easier, so that made it even more noticeable. It almost feels like the demon buff spell (empower) should cost a soul shard. The spec executes its theme really well, though. Felguard, Dreadstalkers, and a gaggle of wild imps up at most times is a lot of fun, and they get a brief buff visual when you cast empowerment that is satisfying.
Surv hunter seems really fun but I had no idea what I was doing, lol. Really like the new melee animations. Troll with a spear and a dinosaur pet is only a hair below Troll with throwing axes as maximum potential WoW coolness, so I am very happy about it in general.
Enhance shaman I am still sort of torn on. Talent choices change up the flow of the rotation pretty significantly (Lightning Bolt or no Lightning Bolt, spammy rockbiter or charge-based Boulderfist) so I'm not sure which style feels best. I do think it's overall better designed than it has been in recent expansions, though. I also like how auto attacks/WF procs and Storm Strike are your only sources of physical damage, everything else is elemental. It really makes you feel like a shaman and not just a warrior or rogue with a different coat of paint.
Unholy DK has permanent abom pets that you can transform into festergut/rotface so it is automatically amazing. Rotation seems simple in theory but a little more complicated in practice, with juggling rune usage on either generating more pustules with Festering strike or popping them with scourge strike. I'm sure there's a sweet spot there that someone better than me has already figured out. I really like that they left the Shadow Infusion mechanic in as a talent as well, as building up RP to spam deathcoils and thus transform your ghoul (or abom) faster became an iconic part of the spec for me.