How can I change the default Unity keyboard shortcut?
Install
compizconfig-settings-manager
Ubuntu Software Center.Go to 'Unity Plugin', choose General tab (the default tab)
Change Key to open the first panel menu as you like to free your shortcut:
Some more key bindings are in General Options, tab Key bindings. I was using CCSM 0.9.11.2, in future versions of CCSM these options can change.