I've had a Z1 for several years and find it wonderful. When I used a Pentax 67II, the aspherical ball allowed me to adjust tension such that the camera could be repositioned and yet not have any flop issues. The clamp is a bit fussy and seems a little over-engineered, but works fine, unless I'm wearing gloves. I much prefer it to the traditional screw clamp on my Acratech head, where I'm never quite sure if the camera is secure.
My only real criticism of the Z1 is that it should have two cut outs in the base to allow the camera to point down. As it is, to shot down, the tightening knob must be on the right side of the camera, requiring you to reach over with your left hand to tighten since your right hand is holding the camera - very awkward.