My former commute was short, about 13.8 miles round trip. I did wear full cycling gear because I can't imagine riding in anything else, especially jeans. Plus, the way to work was mostly a climb, so i did get sweaty. I brought my clothes to school the day before and I keep essential supplies (face soap, gel, wipes, and deoderant) there. I carry my make up and lunch, along with my reading glasses in my seat bag. I also wear a camelback, with the bladder taken out, for any papers that i have brought home to grade.
I did buy some cycling capris from Prana that I wore all day a couple of times last spring. They are expensive, but they look nice. However, I did feel a little sweaty with them on all day.
My new house is about twice the commute and involves going 2 miles more out of my way, because I usually drive through a major rotary (traffic circle). Since I have to be at school so early, I don't think I will ever be able to commute, because it's just too dark, it will take much longer, and I won't ride in the dark.