I've been commuting for 6 years using an REI Trail 25. It's holding up well and is pretty comfortable, although my commute is only 5 miles one way.
The current Trail 25 looks like it's been updated from the one I have - whether it's an improvement or not, I don't know.
Before I bought the T25, I looked at the REI blaze yellow commuter specific backpack, but it was way heavy.