A cyclocomputer probably would have prevented my knee problems.

My first four years commuting I timed the 9 mile ride to work uphill with a watch. It was fun to see my times improving. As I got stronger, I shifted to higher gears and my cadence reduced, causing a knee cartilage injury. After two months off the bike and some physical therapy I'm finally recovered. Now my Cateye Astrale 8 displays cadence in big easy-to-see numbers. Plus I'm faster now that my cadence is always above 80. Commuting 90+ miles a week at low cadence can eventually damage your joints.