If I have a commuter custom made, it'll be titanium. What I like about running errands on my Litespeed is that I don't worry about leaving paint behind or it getting scratched up parked in a rack. One night I was locked in the cemetery and lifting it over the black iron fence, I scratched the top tube big time. Buffed right out with a Scotchbrite when I got home. I was so glad I had the Ti bike that night.
I've also found that brushed Ti is pretty much invisible to the criminal element around here. When riding one of my painted bikes to work, I'm routinely offered a few bags by cornerboys. (As in, "Nice bike. I'll give you five bags for it.") When I ride by on the Litespeed, nuthin'.
I also commute year 'round, so the fact it won't corrode is a plus.
Stainless shares these qualities--for the most part. Certain stainless tubesets require paint for full corrosion resistance. Most do not, and are fine unpainted.