Unit testing is teh suck, Urr.
wilshipley.com
wilshipley.com
A lot of programs are, in fact, used by other programs. Such programs are generally called libraries, and unit testing can be exceptionally useful for avoiding regressions in them. When testing a library, you can't really get around writing code, so why not check that code in so you don't have to write it again?
But I also think that certain automated frameworks/tests make life easier for everyone, if they're managed well. At a minimum, they can serve as a sort of de facto specification in cases where the system lacks adequate documentation (which is the case more often than we might like.) And as others have mentioned, unit tests serve a dual role. Even if they're not great at finding new bugs, they have some value as regression tests.
But will it? No, I do JavaScript development and unit testing just check the output of the functions. Most of the time, all I do is DOM manipulation, function returns special values, problems like Ajax.
Unit testing is really poor.