A young lad asked a friend of mine this very question on a spring ride when he read the back of a jeresy on the rider in front of him. It means it just works...period. And, in most cases, you can rebuild it to work like new when it breaks down.
After hearing this story, I was reminded of other bike related stuff that just seemed to work, besides the wool jersey (which never seem to go out of style). The one piece of equipment that every rider should own is the Silca pump. I have had my Super Pista since 1993 and it has preformed almost as well as my record groupo over the years.
A few years ago I was at a race when a friend asked if he could use my pump. Then he proceeded to struggle with the pump head and the worn washer, I had the intentions of replacing the washer the night before. A few weeks later at another race, he asked if I had a pump again. When I retrieved it from the trunk he refused to use it, then he asked the persons in the car parked next to us if he could use theirs. I ask him how many pumps he has had, and his reply was four over the last 5 or 6 years. My brother once told me that he refuses to by Red Wing boots for work. When I asked him why? his reply was "I like to buy a new pair of boots every year and if I had a pair of Red Wings, they would not wear out." This must also apply to some people when it comes to pumps.