yeah a lot of people use M4 for in-game voice-activation, but i only used those buttons for browsing as well.
and now that i'm sometimes using the WMO and G100s, i've gotten used to using ALT+left or right arrow, or just right click -> back/forward. even when i use mice with side-buttons, i just forget about them and use those shortcuts anyway..
side-buttons are almost always in the way of how i grip, i think the G400 is the only exception to this. maybe the IE3 as well, but i don't even remember (it's been a while!)
thanks tp4tissue, will check it out!