There is no true "off" other than unplugging the thing. As mentioned there's a standby but it really doesn't do much. Even in standby it's hot enough to fry an egg on.
Its a shame that the only time you see that cool "start up" video is when you unplug the unit from the power and plug it back in. Apple needs to be more "green" and put a power switch in the software so you can turn it off.