I have upgraded to Mint XFCE 6, and noticed a second thing not working on my Compaq R4000 laptop (the other is the volume buttons already posted).
I do not know if its a xfce specific thing, but i know it worked well in ver 5 for xfce and gnome. The scroll bar on my touchpad does not work. Is there some way i can set this? The default behavior before worked well, but now does not do anything, aside from move the mouse.