I've used my daughter's Columbia Treadlite 22 liter. It's back draft suspsension system is very well designed, and the pack is very light. It's a little small if I want to carry a lap top along with the other things I would normally pack. It's not specifically designed for bike commuters, but perhaps for the money it's a better value than the Ospreys or Deuters.
I use the Camelback Mountain 14er. Vented back and plenty of space for clothes and food. I carry water on the bike but use the water bladder when I use the pack for hiking. $100 and couldn't be happier with it.