My DM has said that we're free to play psionic characters but we'll be some of the few beings that use psionics - only the Illithid use psionics.
Plus if we want to play psions, we're responsible for learning the rules, not him. (Although he does have a copy of the PsiH, he'll read it if he has to)
Were I DMing, I'd use it as it doesn't seem overpowering and adds a certain flavor to certain monsters.