Hi,
I got an email from Carolyn the graduate admin at Northwestern. Here is what she said
"No worries about your inquiry, I understand that people are very anxious to know their admission status. We have sent the first group of offer letters out. What I can tell you is that the decisions are still being entered and will show up in the online Application website (Apply Yourself). Most of those decisions should be viewable by next week. There is a 48-hour lag from data entry until viewable, fyi.
Please let me know if you have any other questions. "
I think it was a regret letter hidden in nice words.
Hope it helps for those still waiting on Northwestern.