I remember someone like achow, nullius or theymos saying that right now, you need that both parties are online, otherwise it wouldn't work, which is a big fail and will never get anywhere when it comes to mainstream adoption, but then again, I heard that they are working in ways to mitigate this and avoid needing to have both parties online at the time of the payment which is just ridiculous, it will never catch up, people don't like that, they will most likely resort to third party stuff which will come with a decrease in privacy unfortunately. I wish there was a way to leave the transacion "on hold" until the other peer connected or something.