Stability is key.
No one likes using a tool that crashes, hangs, or acts in an inconsistent way.
Unfortunately there are (virtually) no unit tests for ZAP, one of the standard ways of improving software stability.
There is actually one regression test, based around the API: https://github.com/zaproxy/zaproxy/blob/develop/src/org/zaproxy/zap/junit/TestDaemonWave.java
More unit tests should be written as the API is developed.
However we really need a set of unit tests which drive the Swing UI - any suggestions, or experience with: