Tread lovers, unite! I just nabbed one of these off Craigslist for $15. New, they're ~$48 most places. Very cool toy, solidly built, with gorgeous heavy rubber treads. Never seen such beefy treads on a toy. Comes with a nice educational "mission" manual and a tape measure to accurately measure and plot a course. There's a calibration routine for precision turn adjustments, so clearly there are wheel (tread) encoders. Plenty of fun as-is, or IMHO a good candidate for hacking. The treads scream Wall-E to me. Obviously it needs a flamethrower and maybe higher voltage for more speed/power. I can't beat these well-done videos.
"When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."
- Pablo Picasso