http://www.youtube.com/watch?v=Ias1yKLSHxI
http://www.youtube.com/watch?v=tjQPpWEXcOU
http://www.youtube.com/watch?v=WqMevxSKiCQ
The environments are incredibly detailed, (with the high speed you'd expect things to look muddy if you slow down and take a close look, but they still look crisp and vibrant) and there's plenty of really nice effects going on and almost no visual flaws at all. I just finished the game yesterday and I reckon it takes the cake as the Wii's graphical top dog.
What say you?