How do I disable the long press Super key from showing the shortcuts window?
Solution 1:
1) Install Compiz-Settings-Manager (sudo apt-get install compizconfig-settings-manager),
2) Go to "Ubuntu Unity Plugin" > "Experimental" and uncheck "Enable Shortcuts Hint Overlay".
Solution 2:
If I'm not mistaken (too bad I'm not in Ubuntu right now to check it out), you can also use Unity Tweak Tool to disable the shortcuts overlay.