The book does reference a shitload of studies, however one seemingly appropriate criticism I've read is that the studies are referenced and used beyond what they were intended for. For example, insulin spikes in the morning therefore delay your nutrient intake - the premise is solid, but does delaying breakfast really cause you to burn significantly more fat? Does spiking insulin post workout really cause huge changes in muscle repair? Subtle changes, perhaps - but it's not quantified anywhere.
I doubt it makes huge changes, I've only been on it a few weeks. I'll be coming off it tomorrow, being generous and saying I build 20% more muscle, 20% less fat on it - it's not worth it to me to feel so dead during the day. I need SOME carbs.