To our GMATClub friends still waiting for their interview invites, I hope this bit of information might be helpful in clarifying the speculation about the number of invites sent out so far.
During the first hour, there were originally about 290-300 interview spots for Boston "alone" to choose from. After a couple of days, we see only the "120" Boston spots mentioned here. I guess this "120" number comes from the current updated webpage, which no longer lists many taken spots. For instance, almost all the spots for the first week are no longer listed as taken - they've just simply disappeared. So I think "120 spots for Boston" is not accurate, it's closer to 300 spots with 90% taken. There are many taken spots that no longer appear now.
I can't say about other locations, but I'm pretty sure about the Boston number. Anyway, don't lose hope, guys. I hope everyone here gets their invites soon.