Sorry, but no experience on F. I guess we're talking about long-hauls flights here? I've also included experiences from short-hauls.

AY J-class: long-haul seats could be better (comparing to what QF or CX is introducing). Food and especially wines are good (with the nice Iittala glasses). FA's are usually attentive but sometimes a bit cold. Short-haul seating is awfull but service is OK.

BA J-class: CW seats are OK if you're less than 6ft and haven't got too broad shoulders. A soft duvet instead of the blanket. Food and wines could be better (especially short-hauls). FA's usually friendly and attentive. Good amenity kit and lounges (good that they have also an arrival lounge). Short-haul seating same as AY, food not very impressive.

QF J-class: I've only experienced long-haul with old J-class. Food and wines were good. FA's attentive and friendly with a relaxed attitude. Amenities were OK.

After March, I'll be able to give my thoughts on CX and LA J-classes.