I opened the AA executive and am cancelling my Amex Plat when I return from Europe. I'm all in on AA/US, so the Platinum card and MR in general make no sense for me.
The Plat was very useful while I had it. $400 in AA gift cards, global entry credited for me and for my wife (TSA precheck is amazing), and we got 50k bonus points. Listing all that makes me feel a little bad to cancel, but I wasn't spending anything on this card and can't make use of the vast majority of benefits if offers now. More cent lounges would be awesome, but the ones that exist now don't do me much good.
Perhaps things will change in the future, but for now the benefits of the AA Exec are tailored to my exact needs.