I'm running 10.04LTS inside VMWare Fusion on a Mac.
The [command] key (aka [windows] on many keyboards) is almost always behaving as if it was [ctrl], even though I done anything explicit to request that behavior.
In fact, in SystemPreferencesKeyboardLayoutsOptionsAlt/Win key behavior, 'default' is chosen (rather than the 'Control is mapped to Win keys' option). However, choosing other options there do not seem to change the handling of [command], at least not as tested in the SystemPreferenceKeyboard Shortcuts app. (No matter what I've tried, [command]-x is always detected as [Ctrl]-x in that app.)
I've tried:
various options under SystemPreferencesKeyboardLayoutsOptionsAlt/Win key behavior
toggling the VMWare Fusion Preferences KKeyboard & Mouse Key Mappings setup which claims to map '[command]' to '[windows]', and restarting the VM in each position
the xmodmap lines suggested at https://help.ubuntu.com/community/MappingWindowsKey
And yet, it's clear that all Ubuntu apps aren't merging [ctrl] and [command], because in 'Terminal', [shift]-[ctrl]-c will Copy, but [shift]-[command]-c will not.
If the [command]/[windows] key was recognized as anything else ('Super', 'Meta', 'Hyper'? I don't care as long as it's not 'Control'), then I could achieve my real goal (which happens to be enabling CMD-based cut/copy/paste in PyCharm, while leaving CTRL-X/etc available for emacs-like bindings). I think any solution which manages to make [command]-x appear as something other than [ctrl]-x in PreferencesKeyboard Shortcuts will probably do the trick.