I have bought some to try.
No way would I use it waterless on one of the good cars, but I have had a quick experiment on the already clean 911 (Seal Grey Metallic)and the results aren't anything special.
Next up I shall give the Ute a quick sluice down to get rid of the worst of the last two winters mud, let it dry, and then see what happens when I use it waterless. I'll try for pictures too.
The one downside I have found so far is that it is hard not to get some overspray on the glass, and wax on the windscreen is not a happy combination.