I always liked the idea for my fantasy settings; it's a flashy magical effect, which in many ways I eschew, but at the same time, it's more of a martial artist, Zen kind of thing, not the stereotypical wizard with his flash-bang spells. I'd long had the soulknife as an optional class available in the DARK•HERITAGE setting, and in fact one of the main protagonist characters in my very slowly progressing novel is based around that idea too.
Perhaps it's somewhat curious, then, that I'm now leaning towards using another class altogether to represent it: the Jedi Guardian from d20 Star Wars Revised. In fact, in most respects, this is actually a more complete class; ready to plug and play without any more work, than the soulknife is. True; the Jedi focus is around using a lightsaber, but converting the lightsaber into a mindblade is mostly just cosmetic, and almost everything else is ready to go. I've already got a Defense bonus. The whole Force powers thing is quite a bit more involved (and useful) than the soulknife's very minor access to psionic powers. In fact, in most respects, the jedi guardian is a slightly more powerful version of the soulknife. Since the soulknife is widely considered to be underpowered, needing (at least) the adoption of a Fighter BAB progression to hold its own with other classes, I don't see this as problematic. Although my own playtest experience is fairly slight, in general, the jedi guardian is not considered overpowered relative to the other Star Wars classes, some of which are almost word for word identical to their D&D analogs (fighter vs. combat specialist, for example.)
Of course, one of the most important flavor points about the jedi and the Force is the whole light side and dark side dichotomy. I'm interested in having my first NPC who will feature this class be a "Sith lord", so I intend to use plenty of dark side powers, but in general, I don't want to get into this dichotomy for my campaign. I want to use the mechanics, but make them morality neutral (after all, one of the most notorious dark side powers is Force choke; and Luke uses that on Gamorrean guards in Return of the Jedi.) So, although it's been a little while, I'll need to re-read the jedi and Force powers rules again in more detail, and probably modify them somewhat to make them more value neutral without such a strong good and evil component. And I'll also need to think a little bit about the mindblade; if having it always accessible (instead of being something that can be lost or taken away) makes them potentially a bit overpowered, and if so, should I weaken the damage it does slightly or something.
Anyway, when complete, I believe I'll post my revised rules for using mindblades, more based on the jedi guardian class than on the soulknife class, on my mechanics wiki.