I use the POWER or HOME buttons to turn on the device, and that's about all.
Zmooth provides a right-thumb swipe for RETURN, HOME, and MENU (never got OFF to work). I use Circle Launcher to create two barely visible spots on the Home screen; one evokes a 10-contact circle, the other a 10-app circle. That covers 90% of who I call and what I do. For OFF, one of those apps is ScreenOffX.
Works for me, and I need a hardware button rarely.