one thing i don't like about D&D4e that i'm hoping to see in pathfinder is having a chance for magic or power to go wrong. you know how raven sees the future but misinterprets it? psonics and magic are more fun if there's an "uncontrollable" element. i want to see lower level characters fail on an epic scale -- even if it's my own darn character!
also powers should be a growth path dependent upon the level of the character. luke skywalker can't focus the force enough to lift his x-wing from the swamp, but yoda can. it's more "believable" in an FRPG setting if greater powers are bestowed on those with more maturity. nobody really wants the imbalance of a disintegrate spell at lower levels. but I bet more people would enjoy seeing psychics set things on fire by accident at lower levels, tee-hee.
d&d has never handled psionics well, but if we approach it as another power source, i'm fairly certain that it should NOT follow a strictly vancian system because that's limiting. perhaps using points is the best way to go, because in most of our modern myths, using psionic powers wears down the user (firestarter). i dunno, maybe divide psy powers into classes (reading minds, force power, moving objects, telekinesis) and then build up the powers by level (a 4th level psy should be better in their primary school of psionics than a 1st level, but should have access to the other schools).