Looks relatively easy to build (i.e., inline skate wheels, platform and mount your exisiting pan/tilt head. On their top of the line, it looks like they put a hydrolic lift on it. I would be interested to see how they work that. Overall, I think it is nice that they did this and didn't overcharge as the P&S Skater is. The Skater is a cool device but not for the price they want. May be a rental of the Skater could be in my future but definitely not a purchase.
For the price is just doesn't seem worth it to me. In the DIY thread there were people who built these things for like $35 and mounted their fluid heads to it.
EDIT:
I just went back through and found these threads from people discussing this product as well as some of the DIY footage, in case anyone is interested.