People bemoaning the weakness of psions are ignoring, I think, the
REASON for psions.
It's not to replace the party sorcerer or wizard -- a sorcerer or wizard does that.
Psions are quite simply the most versatile spellcasting class around, period. More skill points, better skills, and a wider selection of capabilities that make a single psion able to heal, teleport, affect someone's mind, and lash out with damage and stunning on occasoin, whereas most spellcasters would be limited.
In this light, the MAD sucks, since it forces more of a focus. It's not bad because you *require* high stats all around -- you don't. It's bad because if you're an 'average' character, you get smacked in the versatility area, which is the psion's primary advantage over other spellcasters.
So, IMC, the solution is to keep the idea of discplines being linked to ability scores, just allowing them to use powers they wouldn't normally be allowed to -- if you have a Dex of 8, you can still use Psychoportation powers, and still use them competently -- even if your DC is 9 + power level. Who needs a good DC for psychoportation?!
In a different light, the psionic combat does suck. IMC, it's ditched and replaced with a bonus feat every 5 levels. Which mirrors the more 'natural magic' feel of psionics better too, IMHO. A psion's magic should affect and alter their basic bodily form in more permanent and integral levels than normal arcane and divine magic. Also, they need to be more distant from the sorcerer -- the 'psionic familiar' is kinda lame, and maybe giving them light armor proficiency (or a higher HD?) instead is sensible.
A more stubtle problem could be the difficulty in playing a psionic character in a campaign where the DM doesn't actively consider them. Because going by the default tables, the DM will never roll a psionic treasure, will never uncover a psionic magic item, will never have an enemy with a psionic power stone.....so that doubly sux for the psion PC.
I love psionics, and I use them a lot. But it does need some polish -- some things to make sure people don't mistake them for 'sorcerers with more skill points and no FIREBALL.' Something to make it clear that psionics are a whole different animal, even if they're superficially similar to magic.