ON and OFF hard buttons are ugly to deal with.

Usually, cable TV is the focus of the system. In this context I use OFF to shut down the system and go to the home page. ON gets cable TV going. From the home page one can choose other activities. It drives me crazy, but many users users are comfortable with and expect to shut down before going to another function.

Each user is different. Before I start the program, if I can I watch the customer use their system and push them a little bit to use the system in unexpected ways, I can observe how sophisticated they are and identify potential sticking points that will require some program or behavior modification.

In addition to the customer, one must keep the system friendly for house guests and baby sitters. (And hope that they don't attack the cable box's POWER button -- I don't include a visible cable box POWER button in any of my programs)