I have one in my Bellanca Cruisemaster.
I don't like it. 2 reasons:
You have to push the button for regular large power changes, like take off or landing ops, or in any emergency like deer on the runway or such. This is an extra thought & movement which could cause a delay. I think I have more control with my hand on the knob and my forefinger against the friction lock with a non-vernier unit.
Also, I've had one fail. They jam up. In my case it was a prop control. It just wore out inside. I was playing around, gliding back to the home drome with about 1600RPM, when I entered the pattern, it wouldn't go in. So the GUMP check didn't get the "Prop Hi RPM" part.
The throttle is a very important part of the flight control system, that vernier button gets pushed a lot more than the prop or mixture vernier control.