Hate them! If I never did any shooting except in the hunting field, I'd probably tolerate them. However, I shoot clay targets 1,000:1 over every hunting shot and they are a royal nuisance there and a waster of clay birds. Makers have put them on SxS for ages, probably because it's a "feature" that's easy to incorporate into the double design. Possibly also because of the British habit of having two guns and a loader for driven shoots, the loader passing the loaded gun to the shooter. However, that passing would be even safer with the gun open. It's the first modification I make on any double I intend to keep. It also allows you to let the hammers down without messing with snap caps. Have to wonder how anyone survives tragedy while using a pump, semi-auto or O/U without one?
Respectfully,
"Blue Rage"