Eli Lopian from TypeMock has blogged the case study we did with TypeMock showing how much more productive we are in testing using TypeMock.

We've been vastly more productive using TypeMock than we were before we adopted it. If you get a chance, check out the Case Study PDF. It pretty much says it all. And if you haven't tried TypeMock yet, what are you waiting for? Go get it. You'll like it, I promise.

(In the interest of shameless-self-promotion full disclosure, I'm fairly prominently quoted in the case study. I can't lie; it makes me smile. Can't help but love TypeMock.)