Most of my devices do not have any know discretes, but my amp has them right there on the remote. Power on is the device. That's cool because it saves me a macro step by automatically going to the device I want. Learning them is no problem. "System standby" in the dicrete power off and I can't learn it. It's a Sony reciever if that helps. I think it must have something to do with the way it fires, because you can see the light on the remote flash several time but not in a constant fashion. I do have a power off button for it from another universal remote so it's no big deal if I can't get it. Just sometime creates problems if you are watching TV without the amp on.
On another subject sorta related. To make my Macros without discretes more user friendly for the wife I have programed the f button to jump from any page to a page containing power buttons for all the componants.