Comment #79 works for me, thanks.
So right now the options for users are:
(a) Use the default Ubuntu install of LibreOffice: Your Alt+? keys don't work, so you can't open the File menu by pressing Alt+F, etc.
(b) Remove "libreoffice-gtk": Your Alt+? keys work, but it looks very different to every other application on your system, and has lots of minor but disruptive bugs like being unable to maximize the window fully.
(c) Remove the Ubuntu version of LibreOffice and install the one from the libreoffice.org: Everything works, but it lacks some minor Unity integration, as mentioned above.