Your Mac Life (streamed, downloadable), David Pogue says that Apple intends Command-Option keyboard equivalents to be for system use, citing the Dock and Jaguar screen zooming as examples. My recollection is that Command-Option was always for application use and that the Control combinations were reserved for the system. A quick look through the human interface guidelines (classic, 8/9, X) didn’t provide any confirmation for my memory or Pogue’s assertion, though evidence from Apple’s recent software (which, of course, doesn’t always follow the guidelines) is certainly on his side. In any case, I would prefer that Apple state once and for all that the system will stay away from Command-Option (except for the specifically mentioned equivalents like Command-Option-H) and applications should stay away from Control. Applications need Command-Option because with OS X Apple has co-opted so many of the plain Command key equivalents. (Plus, if an application uses a plain Command equivalent, it should be able to use the Command-Option variant for a related command.) It would be better if Apple reserved Control for its own use because that’s the only way to allow for future expansion of the system equivalents without taking back combinations that some applications are already using. And, similarly, Control equivalents are the only sure way for users to assign global shortcuts (e.g. with QuicKeys) that are guaranteed not to conflict with applications.