I skitched on my SS a year and a half or so ago. I haven't done it fixed yet. Well, I sort of did it once but didn't hold on very long.
However, I used to skitch on my skateboard all the damn time when I skated regularly (before the bikes!) and we'd go fast. It was hairy because if your trucks were too loose, you'd wobble all over the place.
A friend of mine sort of got into a bad accident because of it. He was skitching his brother's car actually (his brother was giving us a "ride" down the street) and he couldn't control himself (I let go earlier since the speed was too much and I started to feel too much wobble) and thus, he sort of slipped and went face down. He didn't get up, he was convulsing - thoroughly creeped out by that.
He was fine though. He was just unconcious and his body was in shock. Fortunately his brother took him right to the hospital.