I originally did my BDD with plain jUnit but I've been looking at JDave lately because it's almost 1:1 to what I was doing with jUnit. It also runs on top of jUnit so it already works on Eclipse and is also easy to configure to work on continuous integration systems such as Hudson. Can't really compare it with others but my experiences with JDave have been good so far.
Oh and it's never a stupid idea to use mocks! They're not tied to TDD/BDD specifically, their purpose is to ease the burden of testing in general.
