I'm a sloucher. I'm slouching in my chair right now. But you won't catch me slouching after a kettlebell workout. That's because keeping a straight back during the exercises is essential, and afterwards (and the next day), it feels better to keep your back straight.
Interestingly, that changes the way I walk, and improves my balance. As Pavel likes to say, Americans tend to walk by falling forward and catching themselves on their feet, and Russians lead with their stomachs, whether they have them or not.
He also said that his instructors frequently receive the comment from students that "you guys all stand the same way." His response is "so will you." I believe it.
So, just one more plus for kettlebells. In addition to having workouts that actually directly translate to movements you might be called upon to do in an average day of playing with your kids or grocery shopping, it also improves your posture. Time to sell my dumbbells.