My wife's car has had Diamondbrite treatment, I am happy with it, her car is rarely washed, never waxed and stands out in all weathers, i am certain it stays clearner longer and looks better than it would otherwise.
On my 997S I would not consider it, I am happy to wash and wax it and I agree it is not the best finish for a car that is well looked after. However many people just want to drive their Porsche and feel washing it is a waste of driving time, if that is you a glaze treatment of some sort may make sense.