a lot of games I use my x8 for have trouble with the default bindings on the extra buttons. most newer big name games (after 2010 or so) seem to recognize them as Mouse Button 3, Mouse Button 4, and Mouse Button 5 but the left/right scroll have never been recognized ingame with the default binding. a lot of games I have to bind the two thumbs, the middle click, and the left/right scroll to other keyboard keys first using the Intellipoint software.
I leave them bound for regular computing to:
bottom thumb = CTRL
top thumb = ALT
middle click = DELETE
left/right scroll = default
seems to speed up most pc work by quite a bit but with gaming I usually use:
bottom thumb = [
top thumb = ]
middle click = \
left/right scroll = -/+
all keys that usually don't effect default game bindings.
I would image a $40+ mouse would have better default support and not lie about how many buttons can be used but we learn as we buy I guess.