I just bought a Logitech MouseMan Dual Optical.
For a long time I was happy with my one-button Apple mouse. But a friend of mine has a Cordless MouseMan Optical and there I experienced the advantages of the multi-button mouse. I especially love the scroll wheel!
The only thing that really annoyed me with my mouse was the extremely long cable. I didn't want a cordless mouse but I wasn't prepared for a cable with approx. 1.5m lenght. (probably because PCs still connect their mouse directly to the main PC unit)
I solved that problem by connecting the mouse to the left USB port of my Pro Keyboard and then the cable goes round my monitor.
BTW: I spent about 40 Euros, which was a pretty good deal in my eyes.