I like this video because of the emphasis on the role our psychology plays in the search for product-market fit. Understanding people/users well - what they mean when they say "this is interesting" is really important. Systematic de-biasing of our own mind is an important idea in this talk.
Richard Feynman's famous conclusion to his report on the shuttle Challenger accident said "Nature cannot be fooled"-similarly, markets/users cannot be fooled. Either a product or service solves their problem or it doesn't. Anything in between needs to questioned carefully and observed (in an unbiased way) closely. Feynman also says "The first principle is that you must not fool yourself – and you are the easiest person to fool". Same idea as Peter's -- and a very important one!
I wish more founders talked about "what product-market fit feels like" (once they found it) - because only with enough samples, new startup founders can better understand whether they have achieved pm-fit. However, I wish video shouldn't be mistaken for thinking: "my Show HN post tanked, so I don't have pm-fit". I think it is worthwhile trying to understand what he means. It is quite clear when you really solve a problem that someone else has. It is also a great feeling.
One of the reasons why finding pm-fit is hard is because there are too many variables. Peter simplifies it to some extent when he says that while searching, one must be clear if you are changing the market or the product. This is correct, but in reality, these adjustments are quite subtle. So paying close attention to these constant/rapid adjustments (stepping back and thinking about them) is quite important.
I like the conclusion of his talk: you will know when you find it.