Losing my old Kensington keyboard means losing my power button. But even though I can't power up from the keyboard anymore, I can still shutdown or restart easily:
Hit CTRL (yes, CTRL, not CMD) and EJECT key. This will bring up 'Are you sure you want to shut down.... dialogue box. Once in there, hit enter/return for shut down or hit 'S' to sleep.
And to bypass the dialog:
Sleep = opt + cmd + eject
Restart = ctrl + cmd + eject
Shut Down = ctrl + opt + cmd + eject