I respect his opinions, but this is not about him, rather HTML5.
His demos provoked uses cases in my head, stuff I would usually consider flash for. I am by no means anti-flash; I know the SWF and FLV specs like the back of my hand. I have annotated wireshark logs of RTP that are almost faithful to the "spec". And most importantly, I am an Adobe fan, and sided with them against Apple.
But this is one of those "top idea in your head" things. Now, after seeing those demos, my mental model of "what flash can do" has been diminished. I will still use flash for microphone capture, sockets, and persistent cookies. But I know now that I don't need flash for audio, video, and interactive eye candy.
Flash has always been a last resort, and seeing HTML5, in this light, is like discovering Qafiya in English:
http://www.ghazalpage.net/prose/notes/arabic_rhymes.html
http://en.wikipedia.org/wiki/Qaafiyaa