Chief among them, being the potentially transformative effects of hallucinogens.
Now, I should preface this with the fact that I have not ever done an iowaska, mushrooms, LSD, salvia, or any other form of hallucinogen, but, I know enough people who have who all unanimously claim the positive benefits that I figure there might be something to it, and specifically the iowaska is apparently very, very similar to the entire Doctor Strange out of body experience scene with the previous sorcerer supreme.
The more I learn about hallucinogens and their effects, the more I'm inclined to view them in a positive light. Granted, my lab partner in high school staring at the screen saver all class and being quite unable to tie his own shoes reminds me of the potential negative side effects of any sort of recreational drug use, I would also put forth that the iowaska experience is far from recreational.
Indeed, I've heard it can be quite emotionally painful and difficult. But, I also hear that you are confronted with the litany of personal faults and the radical responsibility it will take to overcome them.
Sort of a "fast track to enlightenment" if you will.
Of course, if that were the case, then I suppose Strange might be a bit nicer, post-epiphany, but it is just a movie after all.
PS
I once heard a Pranic Healer explain hallucinogens as "tearing open" what is meant to be opened slowly, in a way that prevents them from fully closing again - much like a leaky gut, it then allows things you don't want in, post-use.
I don't know if that's true or not, but I thought I'd mention it.