Shotguns are pretty useless if range is anything further than 8 meters

My main impression was that if I'm carrying a shotgun and I encounter someone I win about 80% of the time (unless they have a shotgun too). Maybe a bit more unless they just gangbang me from behind.

Other than that, I feel that running with a shotgun is better than any other weapon, because you're ready for closed range "surprises", while if you see someone long range, you have the time to switch weapons.