A&#x2F;B Testing is a way to conduct an experiment.  Instrumentation and talking to users is another good way to gain insights, but it not an experiment.  They are two different (and often complementary) activities.<p>Many, many people have successfully used A&#x2F;B Testing.  I&#x27;ve personally used it to great effect several times.  I certainly don&#x27;t make decisions purely based on the statistical results, but I find it to be an extremely useful input to the decision making process.  All models are flawed; some are useful.