I glad I opted for the rear camera instead of park assist after hearing this.
It sounds seriously flawed and a gimmicky waste of money 
So is the camera. The graphics and beeps of the standard parking sensor are more than adequate for the job (giving a good feeling of distance from obstacle) rather than the "toilet roll telescope" view of the camera.
Coped quite well for many many years with just eyes as driving aid but admit to having liked the sensors as an additional aid and in the upcoming R feel the rear camera will be useful for the tighter car parks as an aid
These elements do not slow the process so very useful and does make it easier in the tighter gaps.
Some places that have to stop require pretty quick parking, or you have a stack of cars backed up behind you, so its align and parked in about the same time as the parking assist is still working it out
But one thing never been tempted by is the parking assist!! (though its not an option on the R anyway, bumpers different? so maybe for £150 may have been tempted for gimmick sake,)
