I have to agree, I love Norvig's writing, but I was really underwhelmed with his teaching ability in ai-class. I though Thrun was a much more enthusiastic and elucidating teacher. It's also possible that Norvig and Thrun placed different priority on the course. PAIP is one of my favorite programming books, so I'm really surprised that someone that would write a text so well would have such a hard time getting that same energy to come across teaching.