XPH is definately worth buying. And the rules are easy to incorporate into any campaign. But I agree with the poster above. Especially at the beginning, use the magic/psionics transparency. That will keep the confusion down until people get really used to it. Then if you want to make them different, go right ahead.
In most cases, a psionic character can appear almost like a sorcerer who has the Eschew Materials feat. The person can do funky stuff in a weird way, much like a sorcerer can. But there is no real need to be concerned about introducing or changing rules or anything like that.
I've found that one good way to introduce psionics into a game is to have the villians use some mild psionic feats. The first time the party is chasing a psionic theif type character and they use the "Up the Walls" feat - your players will definately take notice.
Or the first time you use a psychoactive skin the players will take notice and want one.
If you introduce mild things like that first and in a way that the players don't get badly burned by the psionics, they will think psionics is cool without having to feel pressured into choosing between psionics and magic.