We don't have this system on any of our airplanes, so I do not have any direct experience with them.
What I do know about it is that the Canadian operators developed it for use on gravel strips. Some of these strips acutally have a concrete pad to pull the prop over for shutdown (even with this system) to prevent propeller damage or kicking rocks into the inlet. Seems like a good idea; just don't let any passengers off till that prop stops; I'm sure it takes forever without those huge blades going into feather!
Anyone elsehave any direct experience with this?
P.S. If you shut down the airplane with that batteries off, it will do the same thing.