Their agreement with American Airlines (AA) for lounge access ended. I suspect this may have been AA's decision, since AA came out with their own marketed credit card (Citi Executive or something like that - they have multiple) with lounge access. But American Express (Amex) also started creating their own lounges which are free for people with Platinum or Centurion cards (and $50 for others with Amex cards). The Amex lounges are much better than the American Lounges and even better than the Delta Lounges. Amex Lounges are at LGA, LAS, SFO, and I think at least one other place I'm forgetting.

The other big advantage of Amex Platinum is the travel emergency assistance. They will really help you and pay get you home (even if it is a medical evacuation) if you are sick / injured overseas.

Also, FWIW, the American Airlines lounges have really gone downhill at least in terms of free liquor - they are now serving the same bargain no name brands that USAirways used to serve. There is some rumor they may have to revisit this because of all the negative comments.