There's a difference between sparring for competition and sparring as part of your normal training. I think that the competition rules make sparring not nearly as useful as it could be in training. Don't get me wrong, i's fun, it's good excersize, but you're only working select techniques that really only apply to very select situations. Sparring should be part of your practice to improve your techniques and reactions, not a competitive thing. It's the focus on competition and working within competition rules that, I believe, has given TKD a bad rep sometimes within the martial arts community. And it's not just us either, judo has a lot of the same problems.