Personally I think Kensai is a wast of a good level,
Signature weapon; is a wast because you could just buy a good weapon rather then using levels to get it.
Power surge; is cool, I'm not dissing it

All the other ability's are non-scenes and you lose 3 BAB for taking a class with a medium BAB progression. With I would say you couldn't afford dew to soulkinf's low BAB.
What I would do personally with soulKnife is
Race Strongheart Halfling (lose save bonus gain 1st level bonus feat)
Get feats; Point-Blank Shot 1st lv, Two-Weapon
Fighting 1st lv, Weapon finesse 3rd lv, Quick Draw 6th lv
1st level 1 SoulKnife
2nd level 1 Rouge for Sneak attack
3rd level 2 SoulKnife For Mind Throw
4th level 3 SoulKnife
5th level 4 SoulKnife
6th level 5 SoulKnife (Your DM may rule that "Free Draw" can substitute for Quick draw as it is the same thing. in witch case you would not have to take Quick Draw on 6th level and may consider taking lv2 rouge for 6th level and Quick Draw, it will increase the over all BAB but you would lose "Shape mind Blade" witch you may not need anyways.)
7th + levels Whisper Knife from Races of the wild.
This class has a full BAB progression and Rapid Shot that is applicable to thrown weapons is worth it 1d4 (psy Short sword) + 1d6 sneak attack + 1d8 Psychic Strike. (I'm not to clear on the sneak attack rules, I believe you can sneak attack with a short sword, but if not I believe you can just make them into daggers at will or something)
Also you duel wield thrown weapons and if I'm not mistaken you can throw 2 psy short swords at 3rd level from a 30ft. distance.
But yeah, you should look up Whisper Knife