unity or compiz will no longer reserve/block the use of an unused super+key, but at least in an unity session only lasts for current session if set as a custom shortcut.
Seems to hold if set in compiz so maybe that was the only intention of fix
Didn't test in Gs but iirc super+<a key> was ok, don't remember really & no current Gs install

orig. fix-released bug - seems to suggest custom also
https://bugs.launchpad.net/ubuntu/+s...on/+bug/950160

new on possible break -
https://bugs.launchpad.net/ubuntu/+s...z/+bug/1153343