I love trooping with my backpack but it is more of a commitment. Living in NYC and not having a car, the backpack is a pain to take along with a tote, helmet bag and BFG. I pretty much save the backpack for special occasions when I know there is plenty of room, like Comic-con or an outdoor event.
Put it this way, 99% of the public won't even notice that I'm missing the backpack. I mostly wear it for myself and to set myself apart from the TK's even more.