Well, I've definitely arrived too late to this party. All I can say is fortune favours the bold, and that we learn more from experiences that can be improved upon than things that we do perfectly.
In terms of commentary, having grown up as an adrenaline junkie (not so much these days) speed and excitement is everything with these sorts of sports. What Ryo has done for me sums up what I would expect to see - a panning shot which gives the sense of speed that you'd expect to get while performing this sort of sport. Actually, I would have asked to see if they could have gotten some of the carts up on two wheels for a shot - but this really comes down to knowing the sport - not just the photography element of it. And i think I would have liked a wide angle lens to play around with some interesting perspectives as they raced past - but that's just me.
You can't say it wasn't a worthwhile exercise if you got something out of it