Since it would be equivalent to winning the lottery to experience what McKenna claims to have experienced, even were I to go all in and seek it with my entire being, the true value of his sharing, it seems to me, consists in his near complete negation of my own paradigm. If nothing else, he certainly contradicts all that I hold dear; how could that not be a good thing? His 'method' for 'truth-realization' would seem to be one of peeling away the layers of our self-deception; we do not so much prove the truth, as expose it. Take away the untruth and truth is there, he tells us. Though I can't buy into the truth bit, I certainly agree with the method.
One very distinct difference between the Zhuangzian paradigm and McKenna's can be seen in the dreaming motif. For Zhuangzi, one awakens to the dreaming, but not from it; the 'truth' is that we are always dreaming and knowing this frees us from depending on any one particular dream. This is seen in the story of the "Autumn Flood" where the river god meets the ocean god and discovers how small his dream is, yet the ocean god who shows him similarly realizes how small is his dream. Freedom comes in knowing that whatever paradigm we follow it is always going to be a dream. Thus the "well-frog" is 'enlightened' within the confines of his well — climbing out and jumping into the ocean would make no difference at all, except to the dream. McKenna, on the other hand, tells us that we can awaken from all dreaming and know the Truth. Maybe he has, but few are able to do so.
Thus, for McKenna, there remains no mystery at all; 'mystery' is a mental construct, is itself a form of self-deception. I concur, but understand absolutely everything as Mystery, because as a human being who necessarily dreams and can only dream, this is the only interface I can experience. Certainly, for Mystery there is no Mystery.
What's so 'bad' about dreaming? I don’t know. (Isn’t maya nirvana? Doesn’t it all come out in the wash, in any case?) But some dreams are happier than others. (I take temporal happiness as my ultimate value, dreamer that I am.) There is value then in awakening to the dreaming in that we are thereby able to choose a happier dream. Some might find belief in McKenna's paradigm the one that best suits their needs. Enjoy. Who knows, maybe you'll win the lottery. (Or maybe you’ll only make yourself — and others — miserable.)
You can check out Scott's other miscellaneous writings here.