Yes, I saw that following links from this thread, and have spent more of the morning than I should have reading it and the various threads discussing it.

I think the criticism seems valid, and it probably means I shouldn't use the book as a reply to people asking for scientific evidence (like the comment I replied to). That said, I don't think it detracts from the main argument of the book, or the main revelation for me, which is that most people don't realise how damaging lack of sleep is. I would still recommend it to a lay friend on that basis.