Just saw one this past Sunday at the Alameda County Fair. It was okay. I don't know if it was typical, but there were only two RVs in the arena, presumably because of their large size and poor maneuverability. Also, because the drivers sit atop the engines instead of behind them, and because it wouldn't be cool for any high-slung wreckage to spear another driver through their front or side windows, they avoided frontal contact almost entirely.
Oh, and it turns out RVs disintegrate rapidly. I learned that it's not the carnage, per se, but the becoming of carnage that is entertaining. The show was over too quickly. In fact, it ended when one of them caught fire shortly after they lost their radiator. If there were more vehicles then that wouldn't have meant the end of the show. Maybe buses--well built buses--would have been more fun.
OTOH, the only demolition derby I'd been to previously was last year's derby at the Alameda County Fair, which was all cars. So probably I should be careful about generalizing.
