Regarding priority boarding/access benefits:

Just got back from a European trip with 5 flights in the itinerary. Outbound (ATL-LGA, JFK-MXP), online check in at home produced boarding passes with Priority Access notation that worked for counter bag line and boarding, although some employees didn't seem familiar with the perk yet. At JFK, we were looking for a priority check-in line and noticed a small walled-off area with some sort of "exclusive" notation (don't remember its exact wording). Showing the pass, & asking if we could check in there, the "guardian" asked how the priority status was given. We briefly explained it to her, & while showing her the Aadvantage MC, she noticed an adjacent British Airways Signature VISA, which seemed to end her inquiry more quickly than our explanation. Odd.

Returning, AA's site switched online to the British Airways site for boarding passes since the first leg was on BA (BLQ-LGW), & they did not print with any kind of priority notation, even on the first AA flight (LHR-JFK). Checking in with American at LHR, however, produced new passes for the AA leg with the Priority Access noted (again, the counter agent didn't seem familiar with why, but didn't question it). I don't know whether the BA pass would have also had that if it had been the second leg and/or if I had been able to print it from the AA site, or at an AA counter. Another open question for now, I suppose. In any case, it seems to give full priority access, not just boarding, at least on AA flights.