mike-ward Maybe I'm an outlier here but since I turn the appliance (a.k.a. computer) on with the power button doesn't it make sense that I should turn it off with the power button? My coffee maker works that way.
I have yet to see an OS (Windows or Linux) that doesn't allow the user to set the power button to "Shut Down" when pressed. The setting is usually in "Power" or "Power Management" or similar. Pick the action you want (do nothing, sleep, hibernate, shut down, etc.) and go with it. If you select shut down, the computer will behave like your coffee maker
That's not, however, what your OP requested. You requested a two-stage shut down, where pressing the power button once brought up a menu but pressing it twice shut down the computer. I've never seen that in any OS, or on coffee makers, for that matter.
brent [A]ren't all hard boots/shutdowns/reboots rough on hardware to begin with?
By "hard boots/shutdowns/reboots" I assume that you mean something like what happens when you press-and-hold the power button for a while, abruptly shutting down the OS and the computer. I don't think that is harmful to the hardware, but it can sure screw up an OS because the OS did not shut down in an orderly fashion.
Normal power button boots/shutdowns/reboots (setting the power button action through the OS) do whatever in an orderly fashion, just as if you had clicked the selection through the OS. No harm, no foul.