I picked one up recently to try it out. Terrible! Even compared to riding with my backpack on the messenger bag was worse. The weight distribution is lopsided, and yes, on a bike I still feel it, and even more so walking around. The waist strap doesn't prevent the thing from sliding around my shoulder, requiring me to constantly push it back. The bulk of it grinds against my lower back.
Would not recommend one, not at all.