I use jMockit only because of it's reflection libraries in Deencapsultation.class. I actually love Mockito's style, but I refuse to change my code and muddy up my API just so a limited testing framework can get at it. And I'm a fan of testing all my code, so a framework that can't easily test private methods is not what I want to be using.
I was swayed by this article
After a (admittedly large) learning curve, jMockit is now my main unit testing framework for mocks.
