Justin referred to McKenna's comment about meditation being a slow way and ayahuasca being an almost instantaneous way to the same destination.
I drink coffee, had a very few beers and a little wine over the years. I know through direct experience and observation about all the substances. I've taught classes about substance abuse. I've worked with 12 steps counselors. I ran a coffee house and auditioned major performers who relied on various substances.
I think the spiritual experiences are completely different, but how would I know?