Hi Slowrotor,
This particular interleaving helicopter is not intended for speed. It's indented for ease of piloting. -----> more pilots -----> more rentals ----> more craft -----> more production ----> lower cost & higher safety.
Yes, all 2-blade rotors when combined with any type of flap/teeter restriction (offset hinge, hub spring, etc.) will experience 2/rev vibration during horizontal flight, however, this craft has 3 blades.
A friend in Kelowna just built and hovered a simple model of the 3-blade Interleaving this week. He said that it had good stability, due to the precone in the two disks. Next week he wants to build a slightly more advanced model.
Dave