A corollary: we use Java and Python mostly, and when interviewing candidates, the vast majority of them choose to give their answers in Java. I don't ask particularly hard questions, but I find that I usually get a good sense of the candidate by just talking to him as he's working out the answer.

This one guy chose Python, which delighted me since it's so rare. He then proceeded to produce answers much more easily than the average candidate, and he was able to make changes as I suggested them without too much effort.

We hired him but had to let him go after a month, when it became clear that he wasn't as good as I'd thought he was. Turns out it was Python that just made him look smart.

I like Java for actually getting things done, but it's such a vast ocean of TMTOWTDI that interviewing in it seems harder than in smaller languages.