Ken - this is a very thorough review of exogenous ketones in general and the Pruvit ketone product in particular. I agree with most of his points, however, there is a point he makes (highlighted in bold below) where I have doubts.

In speaking with the Pruvit people at the same conference, I asked how an exogenous ketone product would benefit one who was already in ketosis due to a strict low carb diet. I received no plausible answer other than to point out I could cheat and get back into ketosis more quickly. At this time, I strongly believe that producing endogenous ketones through carb restriction is more beneficial and exogenous ketones should not be taken by those on a ketogenic diet, as they might risk their current state of using fat as primary fuel over glucose. If I can produce my ketones naturally, why would I want to change the metabolic pathway to include exogenous ketones and possibly (this is an assumption) shut down my natural fat burning in the process? I agree, lots more to learn before I start consuming what could very well be technologically advanced snake oil!