I did Basic & PSI 7 in 1994. I was smart and skeptical enough to stop there, at the time did feel like I got some good out of it despite the obvious emotional manipulation.
But now 25 years later I'm still dealing with the aftermath of exposing raw deeply buried emotions and issues during the seminars that the non-psychologically trained moderators do not help people actually deal with. I'm only now realizing that my time involved in PSI was a traumatic event in itself, and I need to address with my therapist. No internet back then, but now one can google and easily see the parallels of PSI to other mind control seminars and even cults. I finally understand why my recollections of both seminars have always been fuzzy and indistinct even days after I completed them.
They use some hypnotic techniques- not outright hypnosis, but specific techniques to make people more open to suggestion. Apparently this is common with LGATs. I DEFINITELY experienced the post-Basic "high" thinking it was great albeit expensive, but unable (even then) to recall or describe what we talked about or did specifically that was so great and helpful. Finding out that we were subjected to these techniques finally explains this to me.
Hopefully my real therapist can help me with that aspect as well. I would say SAVE YOUR MONEY and don't give it to PSI, that's all they are interested in.