I have ... feelings ... about psionics, both as not quite fitting the setting (let's face it, late seventies was a lot of Zener cards mixed in with the occult business) and the mechanics.

To be fair, I have never looked at Dark Sun.

I think psionics could be workable, in a certain light, but that's the subject of a rather half-baked and long essay series I have been kicking about for a decade as to how to "fix" many of the issues in D&D in a way that does not result in the Endless Next Edition problem.