Firstly, the breathlessly monotone narration. But hey, the guy isn’t paid to be a presenter.
No, what really gets me is the flickering. Even with colour compensation (which is very neatly done, incidentally), the edge flickering makes my eyes go funny. Perhaps it’s not as bad if you’re using the software rather watching dodgy YouTube video of it, but still… bleurgh. I think I may have to have a lie down.