There's a difference between checking that the code works overall, and checking that each individual component works.
Anyways, I realize I'm in the minority (in many ways..), but I find that if I have a crapload unit tests, then I'm more inclined to not want to change how something works (because then I'd need both new code AND new unit tests - for everything).
To me, that's a bad thing
As an aside, is there any studies that show that the proliferation of unit testing in the last few years has actually reduced the number of bugs and/or decreased development time _overall_?
Ba bow.