I'm worried about whether or not the melee finishers will be only at the end of combat or not, and whether you'll be damageable during them or not. If it's something that can only happen at the end of a combat, and there's no chance of being screwed over by losing control of the action, then ok. If they can happen any time during combat, I'm going to be really annoyed. I imagine it's going to break the flow of combat if I'm in the middle of hacking and slashing and burning, and suddenly find that my flurry of button pressing is going unrewarded.
I'm also a bit sad that birthsigns won't be a part of this game. That's a "it doesn't mesh with the continuity of the universe, since birthsigns in that universe really do play a role in an individual's creation" issue for me though.
I'm in favour of the no-class system, though. In Oblivion setting up your character poorly or not understanding the leveling system until 40 hours in meant you'd be screwed beyond on reason. A good build was meant you had to choose the skills you'd use the least as main skills, then carefully grind minor skills from here to Secunda and back before finally using your main skills to actually gain a level. It was tedious and boring, and most importantly it wasn't fun on any level. The way this new system is set up, you just have to play any way you want, and you'll get more powerful in those abilities without having to mess around with attributes. The whole point of attributes were to define your base damage, speed, health, encumbrance, luck, and magicka reserves. Now you get health each level up, and can add to either your health, magicka, or stamina pool. Stamina now determines encumbrance, weapon skills directly determine weapon damage, and (presumably) speed and luck related upgrades are going to be available as skill tree perks. It's a much nicer system, in my opinion.