Requests for better explanations of identified discrepancies aside, Dialyzer has been extremely successful. It has managed to identify a significant number of software defects that have remained undetectedafter a long period of extensive testing. For example, because of the high level of reliability required from telecom switches, the developers of AXD301, a team consisting of about 200 people, has over a period of more than eight years spent a considerable percentage of their effort on testing. Still Dialyzer managed to identify many discrepancies and often serious bugs. As another example, certain bugs in Erlang/OTP standard libraries managed to survive over many releases of the system, despite being in commonly used modules of the system. Although this may sound a bit contradictory, it has a simple explanation. Many of the bugs were in error handling code or code paths of the library modules which were not executed frequently enough.

Source: Experience from Developing the Dialyzer:

A Static Analysis Tool Detecting Defects in Erlang Applications