Not noticeable at all (I'm testing on a 2 yr old Macbook Pro).
I remember the latency being around 4-15ms depending on the number of hands in the frame. That's very low, but if you compared with 1-2ms latency it would be noticeable. Applications can add additional latency on top of that.
60Hz+ seems good for this type of tech, especially in its infancy. Obviously it would be great to have 1000Hz input like that, or even a touch screen at 1-4ms on readily available devices.
I think I have a use for this if their SDK is good. I'll check it out. Thanks!