I went to the AMEX lounge and was a bit disappointed. It LOOKED like the Centurion lounges in the USA, and the seating was plentiful and reasonably comfortable, but the food and beverage options were far inferior. No staffed bar, and only a few cold cuts and rolls to eat. It looked like they might sometimes have ice cream, but there was none in the case. I heard somebody ask for it, but it never appeared.
I was going to also check out the Admiral's Club, but I didn't make it there (had I been hungry or thirsty, I would have mustered the energy to see if I could do better). I doubt it would have been materially worse, since the BA AMEX lounge was about comparable to USA Admiral's Clubs.