Dodger's had 2 different styles/sizes of Outward Hound packs and I really didn't like them... They are affordable and easy to find but IMO the quality isn't there, not to mention they sit too much on the back than the shoulders for my liking. I was only ever able to pack lightweight gear like poop bags or treats - he could never carry water, toys or leashes without the pack sliding all over the place (no matter how many times I rearranged the gear).
Dodger now has the Ruff Wear Palisades pack - I love it! The quality is amazing, it doesn't shift around and it even fits his bulky blankie. I love that I can remove the pack without taking off the harness and the fact that I don't need to pack bottles of water is also a huge plus...