When my wife got her GC in 2010 the officer that interviewed us said that she was going to make a recommendation of approval to her supervisor. She did say that officially they have to say 30 days for the approval letter and 60 days for the card. However, in reality (as the officer also said) it is one week for the letter and two weeks for the card. I did receive an automated update regarding card production order late the evening of the interview. However, I wouldn't trust the online case status system since our I-130 and I-485 applications where not in the case status update system until a month after we filed.
In your situation, I would recommend making an InfoPass appointment at the field office where you had your interview. Try to schedule your InfoPass appointment for 30 days after your interview date.