I like that Sonic looks like he moves around really zippy and tight. I don't like how jumps have no momentum. You can just drag him around in the air mid-jump. Parkour system looks fun.
The 2D section was awful. Awkward platforming. It looked just like colors and that's not a good thing.
The third section, "Mach Speed", looked stupid. Why force it? Why not leave it up to the player with the new movement system you implemented? What's the damn point of giving better control if you're going to take it away for an entire level?
Are we going to see more levels like the first one? Those are the only ones I care about.
I'm not feeling any hate for the other two levels, but I agree with the basic sentiment that the vast majority of the game should be more like level 1. That seems like the ideal gameplay, and all the new game mechanics from the run toggle to the parkour seem geared for it. Hopefully someone will ask a developer at E3 and we can get a better sense for the structure of the game.
I don't mind if there are other levels with different styles here and there, as long as they're fun and not a major focus. Mario Galaxy, for example, had quite a few themed levels that almost felt like bonus stages... They broke up the gameplay, provided a change of pace, but they weren't that frequent.
The other two stages looked pretty fun to me, but I agree they weren't as cool as the first stage.