Got my passport stamped!
Arrived at the USCIS building at 8101 Stemmons in Dallas at 10:30 AM. There are two lines outside the building - one for those with appointments and one for those without. Both lines terminate at a single counter and the officer services both lines with priority for the appointment holders. If you have an appointment then you get a token and can enter the building lobby.
The non-appointment line was only about 20 deep and my turn came up in 40 minutes. I showed the lady my I-485 approval notice, my tickets for next week and my AP, and asked if I could still use the AP. As expected she said the AP was invalid and I had to get an infopass appointment for processing the I-485 approval and stamping my passport. I then showed her my infopass confirmation for August 16th and explained that my travel date was 4 days before that. She pondered for a moment and then said she'd cancel the August 16th appt and gave me a walk-in token (series E) and told me I'd be called at around 2:30 PM.
Better safe than sorry so I came back at 12:30 PM and entered the lobby. As advertised my turn came at 2:45 PM. The officer was very friendly and the whole process was over in 7 minutes. Submitted all EADs and APs, the approval notice, I-94 and 2 ADIT-style photos.
Good luck to those of you in a similar situation - traveling within 2 weeks of approval. My advice is to go there and give it a shot. Worst case you've wasted an hour and the round-trip to get there.
