Wow, what a find! These are well worth sitting through, but if you don't want to invest four hours, the content of these videos is in Feynman's book "QED". But if you're ever going to spend four hours watching QM lectures, make it these.
Fantastic. Feynman is the most amazing scientist possible - enlightening and (seemingly) approachable, yet still a genius. I can only hope that there will be more like him in the future.
My first thought is the first link has left me with more questions than answers, but I suppose that might just be the nature of QM.