I think it's really important to develop a really user friendly button mapping tool, if you try to find how to do it, you will find lots of obscure testing and modifications that need to be done, that totally scare some people from ever doing it.

For more details I'll refer to some examples;

I own a HP dv6000 laptop and ubuntu runs great in it, as you may know, it comes with a tiny remote control that would be real usefull if you could configure it the way you want it to, so it would work for more than changing the volume.

I also have a Genius 8x6 MousePen, and again, I don't know what each button does, and i have no way to configure it, so when I try to scroll in firefox, i get returned to de previous page, and if I try to right click a folder, I don't know what happens but I'm sure it isnt right click.

We should have a really simple button mapping tool, that allows anyone to configure any device to work the way she or he wants it to.