I just got a Soma Folsom messenger bag from Nashbar... link
here.
I HAVE to have a messenger bag, backpacks are much more sweaty for me, to the point where it's a disaster in the summer. I would prefer better weight distribution, but I can deal with what I've got - not with the massive sweat mark that made me switch after years of using backpacks. I might try to rig it to my Voyageurs rack when it's not raining.
Panniers would be great, but inconvenient for carrying. I'm going to be in school full time and working full time next year, and I really don't want to carrying panniers around.