Perry is highly biased from a particular premise derived from his place in the "traditionalists" movement, that includes other critics of Gurdjieff such as Rene Guenon. Based upon those methodological premises, this seems to be a fair critique. But anyone deeply familiar with Gurdjieff's own methodology will realize that the points Perry makes are not relevant outside Perry's own restricted paradigm-- or at least not within the paradigm Gurdjieff sets forth.
Ultimately, Perry's arguments center on points of belief. He claims that Gurdjieff puts forth that God is not omnipotent, therefore -- ipso facto -- Gurdjieff must be disqualified.
The only reason I put forth that this book is not totally worthless is that it is one of very few that almost skirts the line between the dozen or so ridiculous National Enquirer- level anti-Gurdjieff books, and the hundreds that basically treat Gurdjieff's teachings as sacred scripture. Gurdjieff admonished his students to believe nothing unless personally confirmed. So this book may help raise some questions toward that confirmation.