I do MTB shorts if anything. My ride is so short (3 mi RT) that on days that aren't too hot/humid I just wear my work clothes. Slacks and a tie took a little getting used to, but it's easier than having to change in my office. On top of that the old school 70's saddle on my 3 speed is comfy enough that I don't really need the padding of shorts.

FWIW - I use the MTB shorts on long weekend rides too. I used to be OK in normal bike shorts but I just can't bring myself the wear them right now, more out of a "who am I kidding, I don't race" mentality than anything else.