I've read through the entire playtest document and had some time this weekend while driving to a wedding to think about the class. Here are some of my thoughts:
Overall, I really like the class features, though I think that witch doctor's mask needs some tweaking to address some technical issues I mentioned above. Evil Eye is awesome and I hope that their are some feats or magic items that will make it more potent by inflicting a penalty to the re-rolled saving throw. Now that said, I think that the witch doctor should get the ritual caster feat as a bonus feat; IMO, it makes sense given their traditional role in a tribal society (especially the healing and divinatory aspects). However, the ritual book should probably be re-conceptualized so its not a literal book (i.e. runic carvings on a fetish, mystic tatoos, a necklace with intricate knotting, etc.). I'd start them with two rituals like the other ritual caster classes.
Unfortunately, I was kind of disappointed by the powers (but not all of them). One of the stated goals of the playtest document was to explore the controller role and differentiate it from the wizard, but I feel that the plethora of powers with the fire, cold, lightning, and thunder keywords and damage types really makes the witch doctor seem like a wizard to me. Basically, if you scratch out "Spirit" and replace it with "Arcane," would these powers really look out of place if a wizard used them; IMO, for the most part, the answer would be "No." I would make the following changes to better distinguish the witch doctor from the wizard:
1. I'm going to again look to the traditional view of a witch doctor/tribal shaman to better define them, and one of those roles is of a traditional healer. I think that the witch doctor should be a controller that shades into the leader role, kind of like how the paladin is a defender that shades into leader. A couple of powers with the Healing keyword would go a long way in this regard, perhaps integrated with a few of the encounter or daily powers so it doesn't intrude on the role of the primary healer.
2. While powers with the fire, lightning, cold, and thunder damage type keywords are OK, I would reduce the overall number of those powers, instead substituting in more powers that use the necrotic, poison, and psychic damage type keywords. I would also like to see more usage of the following effect keywords: charm, conjuration, fear, illusion, poison, and polymorph. As an aside, I did notice that there were missing keywords in many of the powers. For example, rolling boulder should probably have the Conjuration keyword like the flaming sphere power, hands of earth should have the Zone keyword.
3. I really like the thematic resonance of curses and I wish that more of the witch doctor's powers inflicted less damage and more minor penalties (not necessarily status effects), especially those that a save can end to better synergize with the evil eye power. I really think that the at-will powers need to be redrawn in this manner, since only one, serpent strike, involves an effect that can be ended by a saving throw.
4. I really enjoyed the fluff that emphasized the natural and spiritual aspects of the witch doctor's powers. More please.
5. Close walls are fine, but it would be my preference that wall powers actually create walls, otherwise, I think that a close blast works fine and creates less dissonance. I also dislike the wall powers that specify a wall of a straight line, but thats a personal preference.