Did a half day onsite. They never collected my NDA and didn't seem interested in it, so I guess I can feel freer to talk about it.
Met with a couple of managers who clearly hated me on sight. I felt I did a good job answering the questions, however, they pretended they didn't understand. They never made eye contact, kept their arms folded, focused on other things while I worked at the whiteboard. Didn't pay attention at all. I stood there for a while, while the guy read his email, then he snapped out of it and began fault finding and displaying a general attitude of contempt. (note: I am an unattractive older American female, so it sure felt prejudicial, but who knows, maybe they are that way with everyone)
Be careful, they will ask you about what you did at former companies. Always always say that you can't discuss it, no matter how cool or interesting it was. They are testing you to see if you will give away company secrets.