At a 6.5 mile (one way), flat, urban commute, I do generally (dress shirt, slacks, and tie). It's really nice just getting off the bike and starting work. If it's very hot I'll wear a light polo or button-up (something breathable) over my tank-top undershirt. This way I can just change shirts and there's no need to change in the restroom - just cool down, wipe down, swap outer shirts, and a shot of body spray to freshen up (I like Old Spice - a little less overpowering than Axe).