My mouse has the two thumb butons, the scroll and the normal 2 buttons. So I guess 3 button mouse? Anyhow...
I make it a point to use the mouse buttons whenever I can. For instance...
Mouse 4 is charge/intercept/shield block, mouse 5 is MS/BT/HS (I really should shift that, but I use shift+S for shield slam and find it convenient). Shift mouse 4 is battle shout, shift mouse 5 is 'Zerker stance. Ctrl mouse 4 is battle stance, mouse 5 is defencive. So on and so forth.
So, the mouse buttons, I find, are pretty handy.