All right... so being a warlock I feel like I should have something to say about the preview that was posted. (click the header for direct link to the forum post) Albeit a bit late.
Truth is, I don't have much to say.
Fel Flame, looks kinda cool. I love the fire ;)
Dark Intent, sounds similar to the focus a mage has. Might be interesting and another proc to work off of. I've always been interested in contributing more to a group in terms of buffs so this might be something to play with.
Demon Soul...ok I have a beef with this. First, the Demon Soul was an item in many of the WoW books that the orcs used to control the red dragonflight and Alexstraza. It was created by Deathwing himself to take over and rid the land of all but the blacks. Seems like a terrible waste of a name for a class spell. Second, the explanation doesn't make much sense to me. I guess until they release what demon will provide what type of "self burst cool down" (whatever that means), we will just have to wait and see.
Soul Shard Overhaul. Pfft. Until I see it and exactly how they implement it I really have no idea. Right now it sounds like a version of the DK runic system. This makes me unhappy. So I'm going to pretend I don't know anything and wait and see.
Curses turned to Banes?? Ok yea I guess.
Demon mechanic changes; Sounds like that combined with the dev chat from last night means more CC. I'm good with that and hope it's interesting.
New Talents; some interesting stuff but nothing great. Shortening CoD would be pretty cool since I use it during all large boss fights.
Mastery; nothing more than I expected.
Fire Direct Damage Increased. Sounds good to me.
Really, in case you couldn't tell, I'm just gonna see how it turns out. All I wanted was stacked soul shards and they're changing the whole damn system around! How happy I am with it will depend on how it changes my game play. I am really worried about being a mage with a pet. I want it to continue to have it's own distinct class feel and all I can do is hope that Blizz will make the right choices.
Only having seen bits of info here and there I hesitate to make any guesses about how it will all work out.