Still waiting on UNC as well. I actually broke down and emailed as I am considering an offer from UConn. They were polite but brief, said they are still "conducting the admissions process" and that I should know shortly. Not really helpful but I guess it means we have a chance?
I work in an admissions office (undergrad) right now and at least with our system the decision is posted online whenever it is processed but the actual notification email sent out goes through the IT department which has a program set up to errr sweep the system at a set time (midnight for us) and generate/send out emails so it really depends on the way the school has it set up.