I would call it a letdown, but sadly, nobody expects much from Sonic anymore.
I hated this game.
First you get to see the first of many many "cut scenes", which are nothing more than unimpressive still drawings with voice acting over them. They are pretty long, and since you're just sitting there listening to some characters talk and looking at drawings, they... stink.
To start the game, you must first begin with a number of training missions, and each one (though short) teaches you one move. Now, it is important to have this type of thing for a game with all new controls, but they could have easily had one longer training mission that incorporated all the moves instead of the five or six that got to be extremely tedious and boring after about the second one. Also, the one that taught attacks really started to annoy because the attack method is so unresponsive... and if you miss an enemy, just one, you have to start over. You're being penalized because the controls stink.
FINALLY, you get to start the game... which is quite boring. The graphics are pretty good, but nothing revolutionary and don't even come close to making up for the lack of game play. You basically run forward through linear levels, jumping over obstacles and attacking baddies. The turning (basically moving from side to side, not really turning) doesn't control too bad, but the attacks (which are done by thrusting the remote forward) are extremely unresponsive and only seem to work about half the time. Apparently you can upgrade the controls by reaching new levels..... yeah, you have to earn good, responsive controls. Also, this game has a GOD AWFUL cheesy "metal" soundtrack that sounds so bad it reminded me of the kinds of things "DVDA" (Trey Parker and Matt Stone's "band") do in South Park... only it's meant to be taken seriously. I loved the early Sonics on Genesis, but like the past few years of Sonic, this falls flat.