I know when I upgrade applications I want to hesitate since some previous upgrades have changed the user interface significantly enough that it does take a whil

I know when I upgrade applications I want to hesitate since some previous upgrades have changed the user interface significantly enough that it does take a while to "relearn" the interface. Mozilla might try to query those who have upgraded to show that "down time" is at a minimum, if seen at all, and one can contribute to the growth of the browser by doing so.