Several things about this mouse make it the greatest mouse ever made.
- The contour to the hand
- Traction (you might say traction is all software-based - not true)
- 4-way scroll wheel
- A single programmable side button
Many companies overdo it on features and design. This mouse happens to be the perfect balance of everything.
I've used it for the past several years and it's the best mouse I've ever used. So I just picked up two more, just in case they ever stop making them.