Akiks,
From all that I've gathered (both from my interview day and this thread), the decisions have probably already been made. For all you know, you might have already been accepted (booyah, think of that!) - but if you were waitlisted, then you would want to put together and send a strong package that will tip the scales in your favour when the time comes. That being said, go with your gut instincts. If you think a letter of intent and an updated transcript would help you now, then send it (just make certain that they accept these supplemental materials first).
One other thing for everybody waiting, I have a friend who's currently at Yale, who explained the waitlist system to me. He claims that there are 3 tiers: tier 1 = very likely admission, tier 2 = it's possible to gain admittance depending on where you are on the list, and tier 3 = most unlikely. I know this doesn't help any of us right now, but when the letters finally do come out...
Finally, has anybody else called recently? Can we get an SDN'er who didn't apply to Yale to call for us and get an update?
once again, g'luck to all.