Inline rifles don't have double set triggers most have decent triggers on them as it is. I am an old fashioned black powder person and have 3 cap and ball rifles all with double set triggers or hair trigger as some people call them. I am used to them and wouldn't own a cap and ball rifle with out it.
My belief is that they make excelent target rifles. But are not needed on hunting rifles. Most of the time, I don't have the time to mess with a set trigger in hunting. However, if you are in open area and have a long shot, it could make the difference to taking game. I live in brushy area and it would not help me.
I've got a cap-lock hawken replica and love the set trigger for target work. Deer hunting one winter though, with thick gloves on, I got a "premature discharge" because I couldn't feel the light trigger. They're great as long as you're careful.
I agree. I really like them. On my rifle, the normal trigger is a pain to depress, and if I were in a hurry and needed to get a shot off quickly, the double set trigger doesn't take a lot of time to do. But I think it is good for accuracy, so there isn't a hard trigger pull to throw the aim of the gun off in in a hurried shot. I also agree with the comment about distance as well. The less the gun moves when the trigger is pulled, the better the shot. But, caution must be observed, so I always leave my rifle on half cock. When I'm ready, I cock and set the double trigger.