As someone who didn't receive an invitation today, I know how the rest of you uninvited feel right now. Sucks, right? I could be completely wrong, but I'm going to share with you my optimistic point of view.
Applicants who received an invitation today have until November 19th to schedule and complete their interview. The next batch (presumably the other "half") will receive their invitations on November 12th, leaving practically no overlap in the interview schedule (you're unlikely to interview on the same week you receive the invitation). Based on the end-to-end scheduling of these batches, I suspect that this is simply a tool for them to evenly distribute all of the interviews. While we all would like to have been included in the first batch, I suspect that there is no greater or lesser chance of acceptance from the second batch.
Congrats to everyone who got invited today - you're in the finals!
For everyone else, have a beer with me and mark November 12th on your calendar