This morning 3.90 km at 3.59 average pace… who needs this exact information? The good uses: I confirmed that my “home 1K” is in fact quite exactly 1000 metres. Further, I confirmed that my “normal” training pace seems to be right now about 4 minutes per km at least in short runs.
Bad use would be to record everything and try to construct a training program based on that stuff. However, overall, I take the numbers as entertainment. Like the songs on the iPod. Like Lance Arstrong giving “feedback”. Like watching my vette’s speedometer reach the magic 200 km/h! Early adopters have noted that Nike+iPod has made them run more, just for the fun of it. So despite all the facts and figures, it all comes down to experience.