Call me lazy, I just copied my post from the "other place", lol.
It looks like it would be fun. Sucks that they say they aren't supposed to go over 10MPH though. Think of the low friction you'd have on the straights!
On the other hand...this wouldn't work out here in MN very well. There aren't really any abandoned or rarely used tracks. BNSF and Soo Line use up all they can. Plus I find it hard to get permission from BNSF to use their track. My father and mother both work for BNSF and I have talked with many people that work on the rails.... I bet they'd crap their pants if they saw something like that on the rails, lol.
This area of MN has some decent bike trails though, so I guess that would be the MN verision of the rail riders.