Psionics Psimplified

[Spatula]

I don't think so. The original design was minimal by necessity, but even it had arcane casters of two different sorts.

Correct - prepared (wizard, assassin, both used Int) vs spontaneous (sorcerer, bard, both used Cha). No longer true with 3.5, of course.

Prevalant opinion in the pre-XPH world suggest the prevalent opinion was the latter. It was commonly felt that making a psion spread their competancy about and gave them a slender selection for high level abilities made the psion weak (I don't perfectly agree with this as there were many redundant powers in different disciplines, but that's how the argument goes.)

I would say limited rather than weak. Especially if you're using point-buy, having more than 2 stats high enough to learn 9th lvl powers when you get to that level is practically impossible. Which severely limits your selection of higher-level powers. Sure, there are some similar effects that can be found in multiple disciplines (there are numerous hold person equivalents, for example), but those disappear at the upper levels as the powers in each discipline become more specialized. And some of the critical effects (dispelling/negation, teleportation) can only be found in one discipline.

Once again, there is no objectively right answer that is going to convince everyone. If wisdom works better for you, then by all means use it. I don't think it's going to break anything.

Well, I don't use Wisdom for all psions, I was just arguing that it made more sense then using Int. Like I said above, I tie the manifesting stat to the psion's primary discipline.