I guess some people's exuberance can turn people off, but honestly its great in my opinion. Why should someone's joyful exuberance for something make his educational content not worth watching? The guy is obviously just very passionate about spaceflight and people who are pushing the boundaries of science/technology. I think 99% percent of the people I talk to approach this kind of stuff with mundane indifference and cynicism, so I think seeing someone genuinely passionate and excited by it is a breath of fresh air.