Call me crazy, but I think there's something cool about a bike loaded with gear.
Whenever I see one, images of someone enjoying life comes to mind. I even feel a little envious, wondering where they've been and where they're going... There's something about waking up miles from home, loading up the gear and heading out on a long ride far from the usual stomping grounds.
As far as bags, I have a hiker's back pack with it's own ridge frame, which makes it easy to strap to the sissy bar. Not to mention, it can carry a lot of gear.