Dan Siroker and Pete Koomen have already discussed the value of A/B testing2 your features, but at Google, some of our larger apps also A/B test their deployments. This means sending out two versions of the product: one that is the desired update, with the baseline being a placebo (your old version just gets shipped again). As the two versions roll out simultaneously to a large enough base of similar users, you can compare one release against the other to see whether the latest version of your software is in fact an improvement over the previous one.
