my commute is five miles.... I generally throw on shorts (gramicci) and a t shirt and put my khakies and polo shirt in my basket. I keep a pair shoes at work. I do a quick wash face with water and change and I am good to go. Once in a while i have ridden in my work clothes, just adding a leg strap, but I prefer shorts in genera and avoid the chain tattos on my khakis.

If my commute goes to the 8 mile and up range I would (and have) wear bike specific clothes. Why efficiency and that is about where I am pushing my comfort limit, especially on hot days, with non bike specific shorts.