It won't let you moneyshift, if that's what you're worried about. It just blinks the gear you attempted but doesn't actually go. You can eventually get the hang of some throttle blips to rev match, too, if that's what you're into - I typically could get it to shift without any jerking motion.
I firmly disagree with the statements that it will mess up your transmission. Many people claim this and make references to someone they "saw" or "heard about" that had problems because of it, but I've yet to see first hand experience with it. I nearly exclusively drove my car in sport shift mode and never had any transmission related issues for the 150k+ it saw until I've swapped to manual.