Ok, played a Witch Doctor, "KingDiamond," from 1-13 last night. I've always like the mage type class. Played a sorc in D2. A mage has been my main in WoW for years. So my first D3 class for the beta was the wizard. But when D3 gold releases? I'm 95% sure I'll be making a Witch Doctor first.
Your first first freebie spell (not really, it's 4 mana, but regen is fast enough that you can use it forever without ever going OOM) is poison blow darts. Kind of meh, but whatever. But when you unlock the splinters rune for it it shoots 3 at a time, each doing 50% weapon damage plus poisoning the mob.
The second free spell is freakING SPIDERS. You throw a jar filled with spiders, when it hits the ground it breaks and the spiders come out and attack the nearest enemies. Just chain cast and it's like that Arachnophobia movie. Mobs are like OMFG SPIDERS E'RYWHERE!
The third you get in beta is frog plague. Releases 3 frogs that hop toward enemies and do damage, I think they explode too, didn't use it too much. Poison darts with splinters rune seems the best for beta.
The "1" key spell you get is these demon dog things, it summons 3 of them that stay until they die, doing DPS and tanking. One of the first passive ability you can get gives a chance on a mob dying for a demon dog to spawn (if you have less than 3), so you don't have to recast very often. There is a fear that I believe is also a "1" spell, but I like the dogs.
The first "2" spell you get is a targeted AoE snare with a DoT component. It looks cool as crap, the ground is all green and these zombie arms come up from the area flailing around. The second one you get is OK, it steals life energy from surrounding mobs and grants you int, but I like the zombie arms better.
One of the early right click spells you get is firebats. Looks like the dude is spitting thousands of bats that are on fire out of his mouth, and it's a conal AoE. You can rune it so it's just one huge bat that goes further, but I feel the un-runed version is better for AoEing down packs of trash mobs.
One of the final abilities you get in beta, and what I really love and sold me on the WD is Haunt. It looks cool, like two spirits barrel rolling around each other as it flies toward its target. And what it does is freaking awesome. 575% weapon damage over 12 seconds. Pretty beast, right? But it gets better. If the target dies while under the effect of Haunt, the spirits come out of the body and fly to a nearby mob and haunts it! So haunt up a bunch of mobs in a pack and start darting them, spirits flying through the air, destruction!
The WD is very warlock-y from WoW, it doesn't have the big numbers and big chunks of health dropping from a mob every few seconds like a wizard, but instead it's just like a steady drain of the health bar, lots of little numbers coming really fast.