I think I heardd a very smart man when it comes to skiing (who has a website where people discuss his approach to skiing) said that a variety of different movements can be helpful if used in the right way. Now I agree with this gentleman that pivot slips as an end, as something to aspire to and to have persent in ones skiing is not a good thing. Having said that, when I was working on opening my hips, this gentleman had me keep the skis flat and had me create rotation only using my hips (very similar to pivot slips) and I very quickly got the sensation of what it is like to have my hips counter and create counteracting forces on each turn. This was a great use of some movements that I would never use and it was very effective in getting the result we were after.
My issue with pivot slips is that it is very easy to turn the skis without usig any tipping of the feet and skis. In fact when you watch them demonstrated by even the best skiers in the PSIA, there is no tipping at all going on. Hence when people learn this and work it into their skiing, they aren't using any of the sidecut of the ski and they are creating rotation with the hips. I don't think that this is even a subtle distinction. It really is night and day. Because many of us think that tipping is the most important and most difficlut skiing movement, I just choose not to ski with movements that encourage me not to tip.
Now that Ron and Phil have left us I can probably mention Harald Harb all I want!