One thing everyone seems to be forgetting is that stat points, skill points and ladder resets (with ladder content, obviously) are completely anti-casual concepts.
The one thing I love about D3 is being able to re-spec on-the-fly. Builds differ between solo and party play, item and paragon farming, monster power levels, etc. I love the idea of skill/stat points, but it has to be free to re-spec. Who would want to level five characters of the same class just to try different ideas?! I don't want to be forced to read a spec guide before I even kill my first mob, and follow it by the letter lest my char gets gimped.
Ladders, and ladder content, are equally as evil. Sure, I loved the rune words available on the ladder, but I hated the fact that I had to organize my entire life around a game. It may have worked ten years ago, but I'm ten years older now, and priorities change. The ladder system was a workaround for a problem Blizzard never found a solution for. I'd much rather see bots eradicated for good.
As for my #1 desired feature, I'd like to see the GAH in-game, with the vendor. It really annoys me that I have to chug along a bunch of items that may or may not be AH worthy, and I have no way to check without logging out of the game.
My #2 feature would be for prices to be determined automatically and dynamically. A neural network could certainly be trained given the amount of data Blizzard already have, and kept up-to-date by the actual auctions both successful and failed. Right now the AH, and thus the game as a whole, benefits snipers and flippers, which is fine for a Wallstreet sim game, but is completely inappropriate for an ARPG.