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What is the fuss about, really? The whole point of positive reinforcement is to reinforce behavior you want, and ignore behavior you don't want. If it's effective in training a companion animal--and it is--why would it NOT help strengthen your relationship with your S.O.? Especially since it effectively trains YOU as well.
Look at it this way. If you resolve to ignore the behavior you don't want, and reward that which you do, a LOT of nagging is going to fall by the wayside. You'll learn not to sweat the small stuff, so when you DO get upset about something, your significant other will pay more attention--because they'll know it's important.