I knew about this as it was a workaround to the striped backlighting issue on some MBPs. However, mine doesn't stay off. After I hit ctrl-shift-eject and release eject, it's dark, but when I release ctrl or shift my screen turns back on.

You can also set a hot corner to sleep the screen. You can even set a modifier key so you don't accidentally sleep the screen when you don't want to. I use cmd + bottom left corner.
This trick actually puts the computer to sleep- not the display alone.
or you can just turn the darned thing off for the night! 😱