Terraces side is nice... but the First class side is horrible.. very hot and stuffy, and the food is never replenished... the BA staff also love using the F class washrooms... dunno why... even when flying in F, I prefer to sit over in the Terraces side....
I disagree though that its nicer than any US airline lounge... AA Flagship lounges are a bit nicer, and UA International F lounge in ORD is way better...