I have, oddly enough, a Sigma and a VDO, the former on the folder, the latter on the road bike. I never use the fancy second odo. I don't know how, and I'm software developer with a Ph.D. Too complicated for me!

OTOH, I *do* run two computers -- I have a Garmin Forerunner 301 in addition to the regular wheel-pickup computer. Redundancy FTW! 14 hours of battery, though, would limit me to using it for maybe 300k rides without a recharge. Anyway, the "lap" button and screen are ridiculously easy to use and are very handy for tracking intermediate distances as part of an event or training.