Guns are are strange beasts, I haven’t quite figured out all the stuff they change when used in Pathfinder. One thing seems to be sure that they are steady source of damage in close quarter combat.
In last session I ran for the group there was combat against a flail snail in dungeon. It could have been interesting combat with all its magic warping abilities but steady damage from party gunslinger cut it short. The poor flail snail has normal AC of 18 and special ability to raise it to 24. Of course it being a big snail it has touch AC of 8…
Needless to say its huge AC (vs. 2nd level party) didn’t do it much good when the gunslinger got to work. With his attack bonus it was either miss fire or hit. The guns don’t do too high damage since you can’t get ability bonuses to them but they hit much more reliably than for example melee weapons. Of course to balance this out there is a cost to use firearms, bullets and powder cost much more than arrows.
Pathfinder seems to work best in melee range, most monsters have no ranged attack ability and with party that likes to fight at range that tends to get boring when the monsters try to charge to melee while peppered with bullets, arrows and spells. I’m trying to decide if I like the Pathfinder firearms or not but what I have seen so far seems to more about ranged combat being very optimal strategy in Pathfinder if you have ways to slow down the opposition or enough room to maneuver. Guns seem to be working like some spells, only defense is hit points, touch AC is rarely adequately high to be a real defense.