Power button stopped working...
My solution was to install Cyanogenmod (other roms may support this as well) and turning on the "Wake with Volume Keys" option. Then I also installed the application "Fix Power Button"
This "Fix Power Button" application allows you to place a widget on the homescreen which acts as the power button to power the phone off. Then simply use the volume keys to wake it again.
Its not perfect, as there are some annoyances like not being able to turn the phone off from any screen (must use the widget or allow the phone to 'time out' and turn itself off)
There are guides on the internet for replacing the button; depend on if you are that adventurous.