Walked in to BWI on Friday, Nov 8 for a renewal interview.
The office opens 2:15 pm. I arrived at 1:30pm and could have been the first person in the walk-in line, but I decided to sit outside on the benches and get some work done rather than stand in the hallway by the door -- this cost me 7 positions :-) At around 2-2:05pm after observing a few others going through the door to the hallway without coming back out, I went in to wait also.
The first agent showed up at 2:08pm, let everyone in to the inner office (there's a love seat that comfortably seats two, 8-9 hard plastic chairs, and a water fountain), and fairly quickly started processing the first 2:15pm appointment while telling everyone w/o an appointment to sign up on a sheet. Several people arriving later with appointments were always taken before anyone who was walking in, pretty much regardless of original appt time (e.g. they took some people who had 3pm appointments)
A second agent showed up relatively shortly thereafter which sped up the processing rate. Even as number 7 on the waitlist I was called up to the desk around 2:40pm. Routine interview, new photo and fingerprints, and said I was all set for another 5 years. I have yet to receive any further notifications and my app still has "conditionally approved" with my original interview appt so if it doesn't clear up soon I may need to follow
this other FT thread
EDIT: approved this morning ^