I'm going to reply before reading the thread, just because I want to see how much I can remember without being influenced by other peoples objections. So this is probably by no means complete:
1) Smaller, lighter, glossier, 'magazine like layout' core books.
2) Core material spread out across multiple books.
3a) Strong instrusion of entirely new setting material into core books, whether than placing such material in a setting book where it normally resides.
3b) Replacement of traditional D&D core setting material with said alternative material.
4) Saving throws replaced by attack rolls.
5) Automatic criticals.
6) Universal critical mechanic now covering all attack spells.
7) Reduced options in skill system (SW:SE like). General reduction in options across the board.
8) Seems likely to have SW:SE like grappling system. Again, general reduction in options across the board.
9) Per encounter balancing as opposed to traditional D&D at-will and per day.
10) Mearls-like 'every class is a spell caster' class design.
11) Although it isn't a problem with the actual system, the marked lack of mentioning fixing most anything I thought needed to be fixed seems to reinforce the whole 'this new game wasn't designed with you in mind'.
12) Dumb wizard tradition names, and the general approach of marrying fluff with mechanics it seems to imply.
13) Touch attacks now resisted by reflex save (removal of touch and flat-footed AC).
14) Save vs. death removed rather than addressed. Indeed, as a general complaint, problimatic mechanics seem to have been tossed rather than fixed, with no indication of something interesting replacing them (at least as yet).
15) New found emphasis on the demonic. Seems to have gone over the top to me. Just not my thing.
16) Probably not a fair complaint because its more of a fear than a complaint, but really rushed playtesting/short production schedule makes me afraid balance is going to end up being worse rather than better.
17) Monsters seem to be becoming more generic in the process of becoming 'simple'. My basic fear is that the whole system will amount to 30 different monster types that you slap two very simple templates on (one race, one class) in some combination (1st level orc brute, for example) to give the monster some small amount of uniqueness. That's nice as a means of on the fly monster generation, and I can approve of that as a tool, but I expect more craftsmanship in monster creation than that. I don't mind a monster having abilities it might not use in any given combat if the description of the monster implies a creature that has those abilities. It means I can use the creature outside of straight up combat as easily as I can in it.
18) Trigger event driven combat system implied by combat description implies to me more mental overhead than before.
19) Wizards losing versitility. Implied diversification of core spell casting classes, and core classes in general rather than unification into a small set of generic classes.
20) Faster leveling (now just 10 encounters rather than 13) in what I already felt was a rushed rate of advancement.