@gauthamthegr8 and others - Some work servers (and other e-mail servers) will actually block SOM's interview e-mails specifically, and not even route them to spam. This happened to me when I applied, and I didn't know I'd been invited until I got a call from SOM 4 weeks later wondering why I hadn't scheduled my interview. That is to say, they probably intended to send you an e-mail, it just got lost in the ether. Either way, you've definitely been invited, and should celebrate!
For all others - don't feel that this means that you need to obsessively check your status. As you've already seen, invites go out on Fridays, so checking Saturday mornings might not be a terrible idea. If your status has changed, but you haven't gotten an e-mail, you can always call admissions to clarify/schedule your interview if that is the case.