I've not checked other than if the button is still being looked at:
To read the state of the top button on the device, read the file: (Where 0=pressed 1=not pressed)
There must be a new or old reference maybe in the chumby scripts directory for this button.
I've been running my Chumby's in Linux mode; and the button didn't do anything in Linux mode. So I disabled Linux mode and rebooted to Chumby mode on the I8 upgraded to C8 (FW etc) devices. I just tested it on one of the devices and the top button when pressed during the playback of a widget brings up a widget top menu to either exit the widget or make a change to its configuration. Sometimes I had to hit it more than one time or hold it for a bit.
So it looks likes working just fine for me at least.
BTW I've speed up the whole booting process a bit by not downloading the control panel with the first initial boot; rather just utilizing whats already there. (its documented here - just changing one thing on one script).