I just did a walk in at Alexandria ASC with no issues. I showed up at 10 mins before 8 and there were about 20 people before me. They sent some folks back to the car if they had cell phones on them. I finished my prints and was out by 8:20... It was very smooth. No one even checked my actual appointment date. They asked for my GC, Drivers licence and the FP notice... They scanned the FP notice and asked me to verify all my information on a screen.
Good luck.
Local DO Washington Field Office - Fairfax, VA
07/30/04 Green Card
04/30/09 UPS N400 to Lewisville, TX (Day 0)
05/01/09 Application Package Rec'd at Lewisville, TX (Day 1)
05/01/09 Priority Date (Day 1)
05/05/09 Cheque Cashed (Day 5)
05/05/09 Notice Date (Day 5)
05/08/09 Rec'd I-797C NOA (Day 8)
05/13/09 I-797C Fingerprint Notice Date (Day 13)
05/16/09 Rec'd I-797C NOA Fingerprint Notice (Day 16)
05/19/09 FP done (Walk in) at Alexandria ASC (Day 19)
06/05/09 Fingerprint Date - Scheduled (Day 36)
06/15/09 Interview Notice Date (Day 46)
06/18/09 IL Rec'd (Day 49)
07/22/09 Interview Date (Day 83) PASSED
XXXXXXX Oath Letter Rec'd
XXXXXXX Oath Ceremony