I don't think UPenn has sent any letters yet because the GSE open house was just last weekend (or maybe this coming weekend, I'm not 100% sure). They say that if you weren't invited, then your chances of acceptance are low. Oh well.
I was contacted and an interview was requested approximately 5 days after the submission deadline. I was told in the interview that there were only 3(!) spots available this year. Yikes.