The biggest difference that I saw is that airlines such as AY no longer can be used for 'A' inventory. While AY doesn't offer first class on their own flights, they do offer it on codeshares (e.g., LAX-LHR operated by BA). While EF still shows AY codes selling 'A', the AONEx rules say AY in first books into 'D', same as business, which makes no sense, but because of this JL refused to reissue my ticket with the AY code in 'A'. I had to accept the BA prime (which earns a tiny fraction when crediting to AA).