@Tozz The button does work as a reset button out of the box
To use it as a standard button or digital pin (P13) you can use a AVR programmer (Arduino, USBASP, Digispark running littlewire, etc) to change the high fuse to 0x5F (though you'll need a HVSP to change it back if you decide you'd like the reset back)
To use it as a soft-reset you can watch for a button press on PIN 13 and then do a watchdog reset
Admittedly - this didn't turn out as we had originally planned in the Kickstarter - we hoped to have this be the default mode, but after feedback felt having the default be a hard reset made more sense, unfortunately, some features have to change from prototype/beta to final device.