I have to say, I'm disappointed to see a step backward in D&D development. D&D Next feels like some bizarre hybrid of 2e and 4e, skipping the most popular edition's best components. Nothing really needed to be changed from 3.5e rule sets. Why bother with a brand new system?
4e had the complaint that combat was the center of the game and that's obviously true. Classes didn't have very many distinctions and tended to do the same damage at every level, just with different names attached to the skills. The introduction of vancian magic seems to have given some distinction and a "work for it" feel to the mage/clerical classes. This is especially true at higher levels where "encounter" powers would have multiple castings per battle.
I truly dislike the step away from variable character races, as I enjoyed some of the oddities that were possible in 4e. Githzerai, Gnolls, Revenants, etc. were rather interesting to play and I feel more "restrained" by the humanoid-only policy.
It (D&D Next) feels very retro and geared toward the 50-somethings players who remember the "good old days". I think that's fine, since they're appealing to a base, but there has to be a new generation of players being brought in and the younger crowd won't remember or care about "how it was back in X edition." There were some glaring problems with the old systems that either had horrible weaknesses or incredibly strong, min/max classes like the 2e Cleric.