Chris Seberino writes:

> I'm on Emacs 24.3 on Ubuntu 14.04 if that matters.
>
> Should it only work on Windows?

Are you using the Gnome desktop? I'm not familiar with Ubuntu's installation  
options, but Gnome uses the super key for its own purposes, and applications  
may not even have the opportunity to process the super key.

Try a different desktop, KDE or XFCE, if possible.