It works pretty well. Transmission through the mount is reduced enough that if I'm careful with my handling, those sounds don't make it to the mics. There's still transmission through the air, though, so if I bang on the camera or press buttons, the H1 will pick up those sounds.
That's an interesting design. Thanks for sharing. I just made one today for my H1. I still get a little handling noise but nothing that can't be controlled.