I use a messenger style bag (a style by Ground Effects that they don't make anymore) for my commute. It also has a stabalisation style strap that goes in the other direction so there isn't a problem with it shifting around. part of the reason I got it was a thought it looked ever so slighlty more 'briefcasy' (ok I know there is no such word) than a backpack and so I use it as my main work bag for all but the most formal of meetings. I find it fine for the normal workaday load of a little bit of reading I had brought home and my lunch, and even gym gear at a pinch. However for heavy or awkward shaped loads (like stopping off for beer on the way home) it is less comfortable than a backback.