In person and behind the glass is my favorite way to watch people use my interface. You can see so much by body language and facial expressions that remote testing can’t provide. I believe every new feature & new pattern needs to be tested with users whether it's 8 people in the lab, 400 on a remote system or 5 in the hallway during a sprint.
One test that was lots of fun for me though, was one I moderated during my time at IBM. I was able to lead a focus group where we had early technology at that time to see the participants answers anonymously in real time. It was fun to say “the survey says!” and then try to draw out the folks who would normally stay silent.NEXT: Standards