Intellipoint Software...

[John]

In Panther:

For those of you who have an MS mouse, I found a really cool feature - 
if you load the Intellipoint 5 software, there are settings so that 
when you depress the middle mouse button (the scroll wheel), the 
application switcher pops up.

Also, as noted on macosxhints.com, you can set the middle button to 
control expose in Apple's standard Expose menu.

Overall, pretty cool features.

Interesting that Apple would implement multiple button functionality as 
they did. And that Microsoft would go as far to add the application 
switcher option.