After being burned by the disaster that was Sonic Riders on the GC/Xbox I was hesitant to try this out, I'm glad I did!
Unfortunately what really brings the game down is a terrible design choice by SEGA in terms of menu's, and menu navigation. While the racing is top-notch you will spend the majority of your time trying to cycle through the countless options.
Overall a great game, if you want a game that you can just pick up and intuitively play, this is not the game for you. This will take a lot of trial and error but if you're willing to put up with some glaring design problems and learn the intimacies of the controls then you will be rewarded with a superb Kinect racer!