Given that high code coverage numbers (85% +) have historically resulted in significantly fewer code defects in projects, why should we try to have fewer UTs and move away from TDD? I generally prefer to pay the quality cost upfront and not have to bother with debugging weeks or months down the line.
And yes, obviously unit testing doesn't diminish the importance of integration / system testing.
It's not about unit testing but rather testing properly. With powerful mocking frameworks like Typemock Isolator or Isolator++ http://www.typemock.com many of these issues can be dealt with even for those who don't do TDD
And yes, obviously unit testing doesn't diminish the importance of integration / system testing.