This video is certanly a drill and on a gentle slope it is easier to make than it seems - you just need to overcome your old habit. For the real skiing, you use both skis, so statements like "pressured inside (or outside) ski" should be read as "inside (or outside) ski pressured more than the other one". And when both skis are used, I cannot help but quoting from www.mamyrin.com: "...the more the pressure on the ski, the smaller the radius it moves with in reverse camber (the less the pressure, the larger the radius)."
Innsbrucker - when you said that the guy on video is not going fast, you hit the point - what should I do when I need to go slow for whatever reason (poor visibility, too steep for me, heavy snow)? I have never envied guys who can ski really fast down a very steep slope because I know I will never be able to do this. But I had envied guys who were skiing in style on a difficult slope by controling the speed and making tight turns. Recipe - unload both skis before the first turn, initiate the turn by applying more pressure to the inside ski (and don't bother about the outside ski - it will never "cross your way") and at the end of the turn, just before the fall line, unload both skis and initiate the next turn in the same way. Try this on the slope which is easy for you (where, in fact, you don't need it) and when you do it confidently you will be able to use it in difficult conditions.
Why so many ordinary skiers cannot ski in style on a simple slope? Because even this slope is too difficult for them, but they dutifully put pressure on the outside ski compensating lack of speed by supporting themselves with the inside leg.
Insbrucker - given your name, you must be based in Innsbruck (I would give up half of my life to live so close to skiing areas). I am coming to St.Anton this Saturday (20/03/10) for one week, join me there - we can discuss and try all this and it will be fun.