Received an invite today as well. I was a little worried as my application went complete on the 25th. But looks like they're cranking invites out. (This makes me feel that application completion or submission date have little or no bearing on the process) FYI - I applied a couple of hours before deadline. I plan on interviewing off-campus.
I would definitely recommend watching the Chicago Booth podcast by MBAPodcaster (if, like me, you haven't had the chance to spend time at Booth). One of the ad-com members clearly outlines the admissions process. She mentions that they look for "sparkle" - God alone knows what they mean by this.
Good luck and Hang tight friends!