I may be in the minority, but I find the 50% unit test coverage not useful, and sometimes harmful. Caveat emptor - depends a lot on the project, and how often you are changing the code and/or the complexity of said code.
My experience is that it's very hard to keep untested code to a high quality level. Any modification that isn't directly justified by a customer feature or a bug fix is frowned upon, because it's hard to tell if it breaks anything ; which means you pile up new features, but you can never modify their design so they fit better together.
When the philosophy is "now it works, let's never touch this module again!", code quality goes down to the toilet.
Better to just do real TDD in the first place.
It is far better IMO to go in with an understanding of where your potential hot spots are than simply adding a test to everything. Sure, in an ideal world we'd have 100% coverage of everything but this field is about tradeoffs and sometimes writing tests simply isn't worth the time it takes to have written them in the long run.