Recently I've been thinking about similar things. I always ride in full gear, however, I've been feeling guilty about driving the car on errands that I could use one of the bikes for. My biggest reservation is the clothing thing. I just don't want to ride without the cycling specific clothes, and I think it's overkill to get dressed in full gear for a short trip. I know it's a psychological thing, but one I'm not sure how to get past.