One of the best interviews I've encountered as a candidate wasn't exactly a pair programming session but it was similar. The interviewer pulled up a webpage of theirs and showed me a problem with it, and then asked how I would approach fixing it. We worked our way through many parts of their stack and while it was me driving most of the way we ended up having a number of interesting conversations that cropped up organically at various points. It was scheduled for an hour and the time actually flew by.

I felt like I got a good sense of what he would be like to work with and he got to see how I approached various problems. It avoided the live coding problems of needing to remember a bunch of syntax trivia on the spot and having to focus on a quick small solution, rather than a large scalable one that you need more often for actual work problems.