Remember CX operates F seasonally on the JNB-HKG route. And even if you get F it won't be the wonderful new suites but the older generation seats.

On BA 747's the consensus on the BA board is that it's not worth paying up for F if you can bag a decent J seat on the upper deck. (And that depends on status or luck). However, you do get to use their super new Concorde Room at T5 if you're in F.

My personal view on F vs. J is that I enjoy trying the F service on airlines enough that the experience is worth quite a lot to me and I'll pony up to do so as long as I can afford it. One day I'll downgrade to J, and be happy about it. But not just yet.