The transition from race to battle to race is unusual, but battles end fast enough and you get a lot of i-frames after, so it kinda works. I began avoiding all oponents and went to the boss at level 1 (bad idea), then I appreciated the combat a bit more.
The game is at its best when you're in the middle of the pack, thinking both about how you're driving and where your oponents are. Were the AI to be a bit smarter, it would hit the spot!