Our current campaign, which has been running for almost a year now, has one psion.
All of the players are mature adults; most of us know each other well, though there are two new guys. Nevertheless, everyone is easygoing and comes to the table looking for a good story and satisfying decisions to make.
All of the player characters are high-powered. Not munchkins, but middle-aged and quite experienced. They had full careers, high ranks, and honed specializations.
The psionic player character is, frankly, overpowered. As referee, I was quite capable of turning that into a plot hook, but without a corrective his character is simply too powerful. In the course of the first session, he was able to use sense projection to see and hear goings on by Bad Guys, and was able to teleport past a Picket and to a grav craft, to enable the players to escape. It was quite a good bit of gaming, although it perhaps made things just a bit too easy.
So far, he is the only psion I put in the game. Soon I will need to add a psionic NPC or two, as adversaries. Two by two, hands of blue, perhaps.
