I agree. Unit tests can definitely slow you down. Testing against high level interfaces or having full integration tests is better. Then the failure is much more likely to be a genuine failure rather than a legitimate change in implementation.

If you have good logging and debugging tools the failure can be quite quick to pin down. James Coplien suggests liberal use of assertions in code which is a really good idea and something C/C++ programmers used to do a lot of. Assertions can then be as effective as unit tests in terms of localising failure.