I wish all TDD proponents understood this. Coverage != Tested. 100% coverage does not mean you have have exercised all possible execution paths through the code.

Also, passing all tests does not mean there are no bugs. Assuming you have tests for all your requirements, passing the tests means only that software can perform those requirements. It does not mean that it will be bug-free, especially if the users try to do things the requirements didn't anticipate.

TDD has the great benefits you mention but it is not the magic bullet so many of its advocates make it out to be.