Dissociatives (e.g., ketamine, nitrous oxide, xenon, phencyclidine, dextromethorphan in cough syrup) are too addictive, too pleasurable, and reliably produce long-lasting delusional states (e.g., as observed in John C. Lilly and Marcia Moore and Tony Hsieh). It is disturbing to read Marcia Moore's "Journeys Into the Bright World" ( http://pdf.textfiles.com/books/journeysbrightworld.pdf ) where she recounts that John…
> unambiguously good: tryptamines (e.g., psilocybin) and phenethylamines (e.g., mescaline).
My friends uncle died jumping off a building on acid. Not one of the psychedelics you named, but having done all three I certainly think such a drastic action is possible on mushrooms or mescaline. Whether this means they aren't unambiguously good is up for debate I guess.