As a emacs user, I always change the caps lock key on my Mac keyboards to "Control". This is in fact a nice built in feature since Leopard. However today I docked my new MacBook Pro for the first time and the Caps Lock key on my external aluminum keyboard (USB) does not send the new modifier key.
Turned out this is a feature. In Lion, you can select different modifier key actions for different keyboards. There is a new dropdown at the top. Select external keyboard and update the modifier key.