Well, I got so caught up in recapping the Demon Hunter Starting Experience (which is really good - lots of fun, not too hard, lots of secrets to discover if you're using Spectral Sight or just observant) that I forgot to actually talk about gameplay.
While there's a good chance that Veranos, my Demon Hunter who is currently chilling in Stormwind after having fended off an invasion of Dun Morogh, is going to eventually go Vengeance as his main spec, I haven't really done much with that other than simply arrange action bars and assign talents.
So instead, we've got Havoc to talk about.
Actually, before we do that, let's talk mobility. You obviously have double-jumping and glide, which Mardum is basically designed to work well with - lots of long sloping paths that you can glide over. Both specs get these two features, which can also be used in combat to get over nasty things on the ground (which any WoW veteran will recognize as a pretty popular boss mechanic.)
All Demon Hunters will start out in the Havoc spec. It think that you unlock Vengeance at level 99 (a little over halfway into the Mardum section of the starting experience) though there's also a later quest that explicitly tells you to choose a spec, though obviously with the new system you can switch specs any time you're out of combat.
Havoc uses Fury as its main resource. You'll build up this purple bar using Demon's Bite, which gives 20-30 Fury.
Your "filler" spender, that you start off with, is Chaos Strike, which does a bunch of Chaos damage and then refunds the Fury spent on it if it crits, making crit a pretty attractive stat.
You'll eventually unlock Eye Beam and Blade Dance, which are also rotational abilities you'll want to use, though these have cool downs (Blade Dance is only something like 8 seconds reduced by haste, so you'll use it pretty often, while Eye Beam has I think a 45-second cool down, meaning it should be used whenever possible, but maybe save it if you've got some outdoor enemy on the ropes already.)
Both Eye Beam and Blade Dance hit multiple targets, giving you some AoE options. Blade Dance hits enemies in an area (I think around the Demon Hunter) while Eye Beam is a... beam attack that hits enemies in front of you - it's channeled and always crits.
You also have Fel Rush, which has two charges and sends you shooting forward, dealing damage to enemies in your path. This is a pretty good ability for both mobility and AoE damage, though like a Monk's Roll, you can easily overshoot enemies, so be sure to be quick on turning with the mouse (something that I could not do on my laptop. Oh well.)
Metamorphosis is your big cooldown. It's actually a combination attack and short-term buff. Hitting it will give you a target reticle. You'll jump into the area, dealing damage to anyone nearby and also transforming into a demon, which increases damage and transforms some of your attacks into other, more powerful attacks. This is on a standard three-minute cool down, so certainly useable on every boss in a dungeon and multiple times per raid fight.
In terms of rhythm, you will be spending a fair amount of time just alternating Demon's Bite and Chaos Strike, though the variable gain on the former and the variable cost on the latter mean you'll actually be paying more attention to your resource bar than most classes.
Blade Dance is on a quick enough cool down that you won't feel like you're missing it, though Eye Beam is on a long enough cool down that you'll sometimes find you really need that burst of damage and don't really have it available.
Chaos Nova is on a one-minute cool down, damaging and stunning nearby enemies. I'm not yet really sure whether this is meant as a rotational ability or a utility cool down. Likewise, Vengeful Retreat does damage, slows enemies, and sends you backwards, and I believe that some talent setups will get a lot of damage out of that and Fel Rush, but will require you to constantly worry about your positioning.
Much as the Brewmaster Monk really embraced the new paradigm of active mitigation, Havoc at least is really embracing the simpler rotation with more dynamic abilities. You won't need forty keybinds to play this spec, but I suspect that that doesn't mean there won't be a noticeable difference between good players and bad ones.
Cosmetically, you'll pick out the normal stuff and then tattoo style and color (separately,) horns, and your blindfold type. Thankfully all of this stuff is changeable in the Barber Shop, so if you pick out a silly looking blindfold, for example, you aren't stuck with it forever. The one thing you can't change is skin color.
You do get alternate skin colors and facial options. Some of the skins have cracks where fel energy shows through, while others give you a sort of scaly appearance. Faces include some with scars or demonic spikes just poking out of the forehead a bit.
And of course all the voice acting is different than standard Night Elves or Blood Elves - not just a modulator like for Death Knights but full on different statements (including Demon Hunter-themed jokes and flirts.)
Demon Hunters do look really cool, though I hope that after we ditch our artifact weapons post-Legion, we get more Warglaive models, because using swords or axes on this class would just seem so... wrong. (I'd love to see some unconventional Warglaives, like the druidy wooden ones from the Shando Illidan skin in Heroes of the Storm.)