Wait... I thought this was something you first learned when you started snowboarding... and was necessary?
Unless... im thinking of just a regular stop after going fast.... and not understanding this trick?
It's not a trick at all. And you are 100% correct about it being a regular stop. What sort of sets it apart is that you stop in a much more dramatic angle in order to stop suddenly at high speed. To stop at that speed with just a normal "stop" would require starting the stop much higher up on the hill so as to not take out the people in the lift lines. Doing it any sooner than that can also cause you to catch an edge at high speed which can be very ugly at best. With a power slide you can stop "NOW". Toeside is the best turn as you can use one hand to help support the angle that your body is in and also allows you to push up your body right away into a gentle coast. If you do it right you can get a lot of gasps out of the lift lines and get grins from the lifties. If you have skiers with an attitude down below (alpine ski racers take note) a well aimed powerslide will create a tidal wave of powder that will envelope them. The result is comical when they try and complain to management about it .
STICK OPPOSITION MOVEMENT
If you want to act 'serious',
then become a skier!