No restaurants yet but I have visited:
The Club @ SJC -- decent, albeit limited food selection.
KAL Lounge @ LAX -- was fairly busy, also limited food selection. I hear it's gotten worse.
The Club @ PHX -- a while ago, using my Diners Club card. I remember it being pretty small.
Plaza Premium Arrivals @ LHR T2 -- wished there were windows. I only stayed long enough to get my local SIM card installed, so can't comment on food, etc.
Avianca @ MEX -- even smaller than PHX's lounge. Not worth visiting, IMO.
KLM @ IAH -- decent as well. Got busier as time went on.