I think that when properly employed, backstops can add a great deal of interest and fun to shots hit around the green. In my experience, the greatest source of backstops are two-tiered greens where if the pin is in the front, one can usually count on a roll-back situation or the ability to play a greenside shot in an unusual direction.
ANGC comes to mind very quickly as a course that, judging by what I've seen on television. Also, I've seen a lot of such features on Mike Strantz courses. I don't know about anyone else, but the ability to chip a ball up slope and watch it trickle back down towards the hole is really neat to me.