I've been playing around on the 7.0 PTR to get a feel for how the new versions of all the old familiar specs are feeling. I don't know how thorough I'll be able to be on this, but I wanted to give my impressions on a few of them:
This one's hard to test without mean things there to hit you, but at least rotationally the spec doesn't feel quite as alien as I expected it to. You basically have Shield of the Righteous ready whenever, but it's now on charges. Your offensive abilities will affect the charges - allowing you to recover some as you go - but with no resource system to watch for, you basically just need to make sure you're using your defensive abilities at the right time. Weak Auras is going to be a huge boon here, allowing you to track whether you've got the buff up and for how long.
The basic impression I got was that there are fewer HoPo generators to hit - no Hammer of Wrath, for example - but with Blade of Justice (or Blade of Wrath, if you take that talent) generating two HoPo, you'll be hitting Templar's Verdict more often now. Judgment has a new animation (think of Maraad in the Dark Portal cutscene at the very beginning of Warlords) and is now really your only ranged ability, though I think BoJ technically hits a little farther than melee range.
Frost Death Knight:
If you've played Two-Handed Frost, this will be a kind of simpler version of that. You only have the one disease now, which should be maintained easily with Rime procs, and Killing Machine only affects Obliterate, meaning you won't be "wasting" it. I might play around with more complicated talents to build on to the spec, but you still get the satisfying blast of a KM-buffed Obliterate. Also, Remorseless Winter has replaced Death and Decay for Frost, which is a little more foolproof as it moves with you.
Blood Death Knight:
This is actually very different, but I kind of like how it plays. Death Strike now costs RP, making it your main RP spender. Heart Strike returns, granting extra runic power when you hit it, so you'll want to use this as your main filler. Marrowrend builds up your Bone Shield, so you'll use it whenever that's fallen off. There's also Blood Boil, which is now free and on three charges with a cooldown, and automatically applies Blood Plague. There's also Death's Embrace, which is a single-target disease applicator (actually, maybe it's this one that applies the disease?) Moving Death Strike to Runic Power actually works out pretty well for the rotation, though once again, I'll have to see what it's like when I'm getting hit by something.
This is nearly identical, especially given that they're going to be adding a replacement for Frostfire Bolt in an upcoming build. (I kind of wish it was just Frostfire, which I thought was one of the coolest looking spells in the game.) Splitting Ice is now a talent (makes sense - as a glyph it was basically mandatory.)
There's a lot that's new and different here, but so far I'm liking it. Bloodthirst is still a major Rage generator, but now Raging Blow also generates Rage. It looks like you've got a chance to activate Rampage on your attacks, which is a series of hits that also enrages you. Furious Strike is a filler when you don't have Rampage and aren't Enraged and Bloodthirst is on cooldown. All the animations here look pretty great.
There's a ton to juggle here, between Demonic Empowerment and summoning Dreadstalkers as well as Hand of Gul'dan. I think you want to prioritize on getting the Dreadstalkers out every time you can, then using Empowerment on them, with HoGD and the accompanying Imps filling in. It's absolutely nothing like the old Demonology, but we knew that was going to happen.
Shadow Dance feels a lot more like what I hoped it would be - less of a cooldown than a rotational thing that is refreshable over the course of your fight. You're still ultimately maintaining one finisher while filling in with Eviscerate, but it feels a bit more shadowy, ninja-themed now. Lots of purple!
There's a bunch going on here, but as far as I can tell, you kind of balance Maelstrom generators (Rockbiter and Flametongue - maintain FT and fill with RB) and pay them off with Stormstrike and Lava Lash (SS on cooldown, LL to fill.) Lightning Bolt is also in there, though I don't know exactly how it fits in. Also, it's weird how few totems I have, but that's not necessarily a bad thing.
I'll try to get to other specs and give my impressions later on.