AMEX plats have been able to enter DL/NW clubs if flying one of the two carriers, but I'm curious as to how it will apply at T4 since it's not technically a NW club, but a contract lounge that NW WC members get access to. I don't even know if AMEX plat holders flying NW can access the JFK T4 lounge as it is.

That said, a beautiful lounge. EI (my entry), LA and a few others use it - In the evenings there's a buffet set up with finger sandwiches and a hot entree of some sort.