Thought I'd add my data point:
Applied: 7/1
Conditional Approval: 7/21
First Available Interview (DC Area): 10/3
Actual Interview and Approval: 8/3 (DC Enrollment Center)
As others have said, you have to check for appointments everyday and you're bound to find one that is much sooner. I think I checked daily for a week before one opened up much closer in time. The interview was very simple and I received my approval email within 30 minutes.