NSC approved, but stamped in SF
Thanks NJ for your response.
I got my passport stamped today at SF INS. My experience was similar to others. Being Monday I expected some delay, but I was In and out within 35 minutes.
Took BART to Montgomery St.
Entered the through the Sansome street (no question asked, just went through the metal detector).
Placed the approval letter through the 200B door slot. My name was called within 5 minutes.
Officer asked for residence Id (my approval was from NSC). I gave my CA drivers license. He wrote down my address on the approval letter and asked me sign and finger print the I-551 form. I then gave my photos, passport and EAD card. He then asked me to sit down and "relax". Needless to say he was very polite.
He took them inside and within 30 minutes called my name to return the stamped passport. He kept the approval letter (luckily I made a copy of it before).
Then I had a nice breakfast at the Deli on Montgomery Street (towards BART).
The key point was that my case was approved at NSC and I could get it stamped at SF with no hassle. I have a CA drivers license, so there was no complication.
Wish you all best of luck.