The impression I got from 15mins in Fire and Sword before going back to warband is that guns, like in real life, cheapen the battle. When you can die in one hit it comes down to luck whether you survive the initial charge. As opposed to primarily "skill" and choosing your approach etc.
Ed: That said, it was somewhat satisfying riding my horse in circles picking off the peasants. Though firing a single shot from my pistol and then reloading for 20 seconds before firing off another got a little dull towards the end.