When I commute to work, I use a single pannier on my rear rack. I'm not carrying that much weight, so a 1-sided load doesn't cause a problem. But even with just a little weight, I wouldn't be happy toting my stuff in a messenger bag.

That said, I do have a Timbuk2 bag that I use when I drive to work and I have extra stuff to take in with me (like shoes on snowy days). The bag is very well made, and if you choose to build a custom bag, there are plenty of color (and feature) choices.

--- Denise