Just two seconds ago I received an email from Yale notifying me that I'll receive my decision soon, either an acceptance or waitlist: "Applicants in this group will either receive an offer of admission or an invitation to join the waitlist." As for the time frame, "We expect to accept a number of applicants during the last two weeks of April and the first week of May as our class evolves."
If I get accepted I'm going to scream.
So I think that if you haven't heard from Yale yet, that's a good thing, because your app is competitive! Hope the info helps. Good luck all.