Yeah, I was going to point that out. You have full knowledge and experience with the D&D system, and I'm sure you've already thought of ten different class combinations that would make it utterly broken. I don't; I just think it's an interesting class that suits the character. If Sky wanted me to, though, I'd be willing to drop these class abilities:
------Quickstep (Ex): The tenken's sheer speed makes him extremely difficult to track in combat at 8th level. On any turn where he has moved 10 or more feet, the tenken's form appears to waver and shift, and he gains 20% concealment as if he was affected by a blur spell. This effect cannot be seen through because it is simply a result of his quickness.
At 17th level, the tenken's quickstep ability improves to the point where another being's eyes are unable to follow his movement, making him appear several feet away from his actual location. He now gains the effects of a displacement spell when he moves more than 10 feet in a turn.
------Haste (Ex): Starting at 10th level, a tenken may act as if he were hasted for a number of rounds per day equal to his tenken level. Rounds per day acquired through another source (such as boots of speed) are added on to the tenken’s maximum rounds per day. The extra attack granted by this effect stacks with the attack(s) granted by the shukuchi, but do not stack with any attack provided by a weapon with the speed enchantment.
------Improved Uncanny Dodge (Ex): At 13th level and higher, a tenken can no longer be flanked. This defense denies a rogue the ability to sneak attack the tenken by flanking him unless the attacker has at least four more rogue levels than the target has tenken levels. If a character already has uncanny dodge (see above) from a second class, the character automatically gains improved uncanny dodge instead, and the levels from the classes that grant uncanny dodge stack to determine the minimum level a rogue must be to flank the character.
------Shinsoke (Ex): At 20th level, the tenken moves with such speed that it defies reality. He is now permanently hasted. Up to three times per day, he can substitute either his Fortitude or Will save with his Reflex save, avoiding the effect with unimaginable quickness. The tenken must be unarmored and unencumbered in order to use any of the abilities afforded by this class feature. He also now cannot be affected by another haste effect.
------The Dodge/Mobility/Spring Attack trio
I don't want to make too many waves, and as you pointed out if I wanted Haste I could just buy Boots of Speed anyway. It's only 5k and there's not that many good magic boots out there.