The battlefield seems more mobile. I like the forced movement rules. I like the increased reliance on different stats -- my concern of a dump-stat was just that, a concern. I think for the casual player it'll be a good thing. Some of the character options I really like -- the ranger's Fox's Cunning, for example (shift 1 square and shoot when someone tries to attack) is a great once-per-encounter option, and far preferable to the old two-step of ready-action, 5' step, shoot. Even some of the abilities I'm iffy on it's more because I think they're a little over the top for 1st level characters; Fey Step is fun and cool, but I think it would be better served at a higher level.
I really like that some of the per-X abilities are "You can do X, Y, or Z, but only one'. That's resource management and players having to make decisions, and I *love* that part of the game. My beef isn't with per-X abilities or even at-will (most of the time), it's the way they minimize the resource management and decsion-making aspects of the game. A question of degree, not their existence.
I really like that they seem to have taken a closer look at the monsters (although I only saw kobolds and a dragon) and given them abilities that differentiate them. I think that kobolds will now play out far differently that goblins or orcs or what have you, whereas before they've largely been interchangeable.
I'm even happy with the mechanics of the healing system. Again, what reservations I have a largely a matter of degree; I like how it works, I just feel for the kinds of games I like it's a little too easy. But the great thing is that would be an easy tweak; just cut down on the number of healing surges a character gets.