My experience at SFO Terminal A a couple weeks ago was identical to your experience at LAX. No hassles, CBP officer was helping a few people with the kiosk and taking a quick glance at everyone's receipts.

My only issue was that as you're walking down the hallway towards immigration they direct everyone into two lines: US citizens on the left (no line) and visitors on the right (massive line), but when you get up to immigration you find out that the GE kiosks are to the right of the visitors so now you have to cut through the huge line to get over to GE.