On the note of a multi button mouse.
I use btnx for my G5 v2 mouse, and it works great. Not only do all the buttons work with not playing with the dangerous xorg.conf (I had to re configure it twice), but you can also use custom commands for each mouse button. Browser and other actions are supported.
You can even have a modifier button, so you can have a different setup for different things.
This works in Gnome / KDE.