I've been to two f2f interviews. The interviews were generally ok, but neither I find them interesting nor challenging. Except that I had really awful experience on the 2nd interview. One of interviewers behave like the person who had self-esteem problems, and tried to show his knowledge instead getting idea of my experience. He kept asking questions on my answers like a kid, even on the things he had less idea than me, and got irritated from time to time. Moreover, I find the questions irrelevant as well. I decided that I wouldn't like to work with that kind of person.