I was about two seconds away from submitting my Sloan application and was doing my last read-through when I had one of those realizations that you have where you realize you've been looking at something so long you don't really see it objectively anymore.
For the cover letter, I had just basically taken my generic "Why an MBA?" essay that I used for all schools and structured it a little differently to flow like a cover letter, but at the last second I realized that they said "Write a cover letter..." not "Write an essay that's kind of like a cover letter..."
So at the last second I added the MIT address and my address at the top and spaced it all out the way you would a business letter, and added a signature at the bottom. Is this what everyone else did? Or do you think they just wanted something that was an essay written similar to a cover-letter.