I've got a couple of friends with them. One of them is pretty experienced and actually had one of the first ones in Mn. They're fun to watch, especially in the hands of an expert.
I've tried several times on three seperate outings and got up for about 20 seconds. The plan is to go out and give it a try on Friday with some guys from work, we'll see how it works.
They claim that yes, once you get up you can stay up as long as you want because there's not much drag. Both my friends love them. One just sold his wakeboard boat because he's now got 3 kids under 6 and just never got out, but he couldn't part with his sky ski.
The good ones are expensive even used. I can't imagine I'd ever feel it would be worth it to drop that kind of cash for one.