Nobody can use my machines. My girlfriend already knows to Ctrl-Shift to change keyboard layouts, but that's on my PC where Windows is in English. On my laptop with Windows in Spanish it's Alt-Shift. Even I get confused sometimes.
Most games I play don't recognize layouts, so WASD doesn't work. I have to Ctrl-Shift before launching a game. And that's on Windows 8 that has per-session layout. Windows 7 is per window layout so if Ctrl-Shift doesn't work inside the game I have to manually configure keyboard.
Copy Cut Paste become Ctrl I, Ctrl B and Ctrl . I think this is not a problem in Colemak.
My first language is Spanish. After learning Dvorak I no longer use accents or ñ (just Alt-164'd that one) so it's a pain when I type something more or less official that can't have spelling errors.
After that rant, I'm still relatively happy with Dvorak. At least I have something to say on job interviews.