I have been an advocate of developer unit testing for what seems like forever as I had my eyes opened up to the value of it at college both through empirical studies and experience writing trivial applications. When automated unit testing came along with TDD (or were the early tools a bit before?) into the Windows development world I eagerly embraced and encouraged their use. It makes development take a bit longer but you remain focussed on only developing what you need. The amount of time in integration, component and acceptance testing seems to be reduced. Unfortunately, I have not been in a position to measure the results but I have not seen the same sort of problems that have continually delayed releases of most projects that didn't do the testing.