Well so far I haven't had psionics in any game in which I've played or been the GM. As a result I haven't spent the time getting familiar with the 3e psionic rules, though after the once over when I first bought the book I found that I did like them better than the previous versions.
In my homebrew campaign world psionics don't exist in the present day, but they did play a major role in the past. My world, Terra Viejo, has its design roots in our own world and as such a lot of its mythic history is based upon our own. The relevance to psionics lies in the lost continent, and fallen empire, of Atlantis. Being a student of Philosophy, in particular the writings of Plato, I've developed my Atlantis according to Plato's model. I won't go into all the details, but Plato's Philosopher Kings are all psionic in my world. Basically the Atlantian empire was ruled by those with psionic power with all others serving them. When Atlantis sank beneath the waves that power went with it, though there are a few genetic holdouts in the hidden reaches of the world.