Yeah, I've always wanted to make one of those. The first one I ever saw was one they had in the Logan International Airport (Boston) when I was about 8 or 9. It was huge, but another cool thing was that it was "musical". I think the creator used xylophone tiles and all kinds of other crazy stuff, so that when the ball was rolling down the track, there would be various "dings" and "dongs". If I knew how to weld (or braze or whatever), it would be fun.
They used to sell a toy kinda like that. Always wanted one, but never got it...