Originally Posted by CXT

I use the Bontrager City Commuter (http://bontrager.com/model/07726), which is similar to this TimBuk2 Tandem and the reason you dislike them is why I love them. Since they are both connected, once I park the bike I can quickly lift the entire thing off and away I go. When carried the center section collapses so it looks like a single/normal bag and with the shoulder strap I still have both hands free to do other things. Off the bike, I found two panniers cumbersome and hated having to carry them around like jugs of milk. The dual pannier setup on the bike that becomes a single bag off the bike was better for my commute. My Ortlieb's only get used for touring duty these days.

I guess the advantage of this type of bag depends on how much walking is involved off the bike.