They are incredible. Every time I have tripped, I've come out the other end having learned more about myself and about how to more appropriately deal with my laundry list of mental challenges.
Also, on a chemical level, I tend to find two to three weeks after a significant dose, it has a profound effect on my depression (which is what studies are starting to suggest is definitely a possible outcome).
Don't get me wrong though, it's fun, but not the primary reason why I would trip the vast majority of the time. And even when I do, I tend to have a bunch of revelations whether I was looking for them or not.