How funny, I was watching the first half of this video over breakfast this morning.
I was a bit annoyed that they used the Nikon rather than the superior 1D X, but I am sure they have their reasons for that.
It sounds like a lot of Sony cameras have an issue with the buffer filling and then slowing things down. Something they need to address.
I would have liked to see him do a test with more than one rider, where you want to jump the AF from to another etc.
Still it was an interesting video, if only because I have never really read about the Panasonic GH4.