I've tried to get mutation testing going on my last few projects. Amusing how little faith/interest there is in this from most of my colleagues. Would be interested in hearing how folks keep this up in a project.
One way to view the problem that Mutation Testing solves is, there's no test suite for the test suite. And so there's no safety net to enable refactoring the test code. It's test suites all the way down.
Mutation testing solves this infinite recursion problem by automating the test-suite-test-suite creation.
I have added it. It got removed for adding to the build time. Never really found many issues, so I couldn't argue to keep it. Did point out that the argument was essentially against testing.