TheTanooki.com has their impressions up of Sonic and the Secret Rings and they seem to echo what others have been saying - the game is fun and the controls work well, despite a few issues. Check out a quote below then follow the link to read the whole writeup:

Right off the bat, playing through the first stage and its numerous side missions, you’ll realize right away that this game is FUN. Sonic and the Secret Rings has by far the most fun control system of all the 3D Sonic games I’ve played, and that says a lot seeing how I hold the two Sonic Adventure games in high regard. That’s not to say the control system is perfect, however. Clearly, having Sonic automatically run forward without having the ability to directly adjust his speed or anything other than his left, right, and jumping motions will not be as precise as having an analog stick. In addition, the motion sensing isn’t all that sensitive.