My list of dislikes isn't that long in comparison to other peoples. There's some stuff I like, I'll admit, and there's some stuff I dislike, but I'd assume that's true of everyone.
Really, this is more or less what everyone else has already said, but that doesn't matter.
Dislikes:
1. The Artwork: I just think the interior art in this edition is really crappy in comparison to the last one. This was really the first thing I noticed. All of the illustrations of the classes and races just seemed really dull and I'm rather annoyed with the amount of recycled art in the Monster Manual. I can admit, though, that I do like the cover design a lot more than 3rd edition.
2. No Barbarian or Druid: I really like the more "savage" or nature based classes, and while we still do have the Ranger, I feel like that niche still isn't really filled. I miss my Druid

. I know they're supposed to fix this with the next PHB with some nonsense about "Primal" Power sources, and that sounds fine, but I'd rather have had it now. Because, personally, I find the Warlord kind of stupid. I don't really think it was necessary to put him in this one. I guess they needed another class to fill the Leader (is that what it's called?) role, but I'd certainly have preferred something more traditional.
3. 3 Elf Type Races: Do we really need three types of Elves? Do people love Elves that much? So much that we get three of them but no Gnomes or Half-Orcs. I don't even like Half-Orcs that much, but I certainly like them more than an assault of redundant Elves.
4. POWERS!: I'd like powers a lot if they weren't all so similar between classes, and if they hadn't made spell casting not feel like spell casting anyway. Well, maybe they still feel like spell casting, but not
D&D spell casting.
5. Everything Feels Artificial: At least, it feels artificial from a relative sense, because certainly everything in a roleplaying game like this is made up. I just mean that everything is organized perfectly and fits in an exact mold and in an exact spot. Some people might like this, and I can certainly see the logic behind in terms of game balance, but I personally kind of feel like it makes the game feel more superficial for some reason. Or like it lacks mystery. It makes magic feel like it's not supernatural. Something like that.
Now just a thought on so-called "Sacred Cows":
I don't mind change, and I personally was looking forward to a new edition, and overall I actually do like this one for the most part. But, I think a lot of Dungeons and Dragons is defined by tradition. It's been around for a long time, and even though it's gone through many changes in its lifetime, there have always been things within the game that stayed put and were always recognizable. You can fiddle with various aspects of the game all you want, but a lot of D&D is its tradition, and I do think that "slaughtering" these "sacred cows" wasn't necessarily the best idea they could have had. Especially when they could have just altered pre-existing things they might have had issues with. Fantasy is about recognizable archetypes, and that's reflected in D&D. The tradition of Dungeons and Dragons is important, and while I'm totally okay with adding elements to it, I think you should definitely think before taking elements away. You need to think about how it will affect the flavor, look and appeal of the game. I don't know, maybe they decided that gnomes won't sell, or figured who the hell wants to play a barbarian? But I doubt it. For me, I don't mind a lot of changes. Vancian casting? Whatever. Saving throws? Go ahead, make them defenses. Gnomes, bards and druids? Why would you get rid of enduring elements of the game and replace them with goofy, cartoonish nonsense like Dragon people? Especially whose females, while supposedly repilian, possess mammary glands.
But no, I do like 4th edition and I'm excited about it. There are just a few things that rub me the wrong way.