I can get a money order at Wal-Mart for 70 cents. I pay my rent that way all the time. I get a receipt with it, and it comes out of my account right then.
My landlady is kind of absent-minded and has waited for two or three weeks to cash a rent check before. Even if you're making allowances for the money to come out of your account, it still messes with your bookkeeping. (Makes me wonder how much she really needs the rent money, too.)
So, for an extra 70 cents, I know the money is out of my account, and if she loses the money order, that's on her. She's lost checks before, but hasn't managed to lose the money orders yet.