this is just a guess, but when I interviewed at Case, I was stuck sitting in the admissions office for awhile and was watching the 2 administrative assistants working and being swamped by huge amounts of data to process. I'm guessing that it will be people like them receiving your acceptance, and they can probably care less about what you say, just be polite, succint, and clear. Don't go into a rant about how excited you are to interview at such an exceptional school, etc etc. Thats my opinion, but I would probably only do a couple lines.