I applied to Harvard as a "why not give it a shot?" It involved ticking an additional box on the Common Application and paying an additional $25 or so. I needed the essays, letters of recommendations, SAT, etc. anyway, to apply to other schools. Harvard had no additional requirements besides them. (Amherst and Dartmouth, however, required additional essays. I ended up giving up on the Dartmouth supplement because I couldn't be arsed to finish it, then have them nag me for another 2 months about my uncompleted application before I finally told them that no, I didn't actually want to apply.)