This.

With my cyclocross race bike in particular, the battle scars are part of what I love about the bike. My favorite is the small stripe of blue paint on my green Major Jake that marks the time I carried too much momentum into the stairs at Alpenrose and had to use the bike (which I had just dismounted and was in the process of shouldering) to protect my teeth from the railing.

My commuter bikes tend not to participate in memorable events like that, so a paint chip from the bike rack or the build-up of road grit in the winter is typically their worst blemish. Consequently, after routine maintenance related cleaning they usually end up looking pretty good.