I saw the trailer, finally.
My opinion: the 2D/3D decision is probably a good one. However, this game seems to be picking up most of the flaws of the Rush system, namely bland, straight-forward level design, the grinding rails that are just plain stupid for 2D segments, and the "Hold a button for invincibility and turbo speed." The latter of the three is the scariest, since, in Sonic Rush, it made enemy placement mean much less, and in the end, very little focus was placed on standard enemies in the game, resulting in generic-looking robots on all the levels, rather than enemies catered to the obstacles on the levels that fit the themes those stages have. If it were up to me, I'd plan a Sonic game all around the enemies and obstacles, but with this speed button, that doesn't matter.
The video sold me on one thing: The game will probably play like Sonic Rush. Now, this is not a terrible thing, Sonic Rush wasn't absolutely terrible as a Sonic game, there certainly have been worse, but if Sonic Team and Sega get stuck in a Rush rut, then there's no chance we'll get games that played like the original five we got on the Genesis and Sega CD. Honestly, I thought the original Sonic Advance was pretty good, too, but subsequent sequels became about the speed and memorizing precisely where to jump with no other alternatives. Maybe we'll see something good come out of this Werewolf stuff, but the actual normal Sonic part of the game already looks boring and redundant, which is too bad.