Once you add in offensive kick (more than just a bit more, by the way, as soulknife enhancement bonuses are quite significant) and a few extra options such as Bladewind and throwing mindblades, I'm not sure what's missing (well, assuming we're not judging by full-caster standards.)Except for Knife to the Soul, I don't see any of the Soulknife's abilities bringing new options to the gaming table as far as the Monk goes. A bit more offensive kick, but nothing to make it more fun (unless higher numbers are all that one's after). Correct me if I'm missing anything.
The ranged option in particular is interesting, as it means that a solo soulknife would be extremely good at kiting.