It depends how you look at it. With a paint guard system like 3M Venture Shield and the like, it can detract from the look of the paint work/car. If you're not fussed, it will save you £££ in resprays. But some people would rather a respray at a cost of £££ each year, rather than the protective cover costs of £££ every few years.
The R8 had some rear panels done due to the amount of stones it slings up from the rear tyres. But you can see where it starts and ends and IMO would detract from the overall appearance.
It also varies massively, a little bit like respray jobs. Some companies are the dogs and you wouldn't know it's there unless you looked closely. Others look s**t, quite frankly.