It seems like tension adjusters are common place, but what is the advantage of getting one? why would you? I know you can go without one, but is there a real advantage in getting one? I would imagine that if you get your skewers tight enough you shouldn't have to worry about it slipping and the chain losening. I saw some dude with the ones that has a bottle opener on the end, kinda excessive but neat all the same. Where would I find them in the city?