John,

Your question is open to many different answers, so I am going to concentrate on a single element.

One element that my users insist on is keyboard shortcuts for everything. For instance, you should have at very least hotkeys (ALT+C etc.) that activate all of your buttons. After that, many of my users insist on being able to use the function keys. For instance, if a user wants to use F3 instead of ALT+C, then you can put commands into the form's Activate method such as ON KEY LABEL F3 KEYBOARD '{ALT+C}'

Hope this helps, I'm sure you'll get plenty of replies.