I have a Contour Mouse (and a Slimblade, L-Trac, and Marble Mouse).
The 17 degree tilt on the Contour is more noticeable than it sounds, and is close to the 20 degree tilt of my Kinesis Advantage keyboard. I had worried that the thumb scroll wheel would be awkward, given the thumb only has two segments and may not be the best digit for scrolling. I think they spaced the notches in the thumb scroll wheel sufficiently close that it doesn't really matter though, and I like it, to the (limited) extent that I like scroll wheels.
I very much like the proper middle button (I'm a Linux geek, and use all 3 buttons extensively), and think it's a rather comfortable mouse overall. I would not get the contour for gaming though, as it's a bit awkward to pick up with just the thumb and pinky, and holding it with the ring finger on the outside it not only awkward, but reduces the utility of the 3rd button.... I think they recommend just tilting the mouse rather than fully lifting it up, but it drags badly when doing this...
For all the things I like about the Contour, the Slimblade is my daily driver.