Agree with most of the points posted already. I think you just have to try it so you can decide whether it's worth it, and unless you get lucky, the only way to try it is to buy it.

BA WTP is the only premium economy product I can sleep in. I've tried CX, QF and LH and I can't sleep in those seats for some reason (I haven't compared the specifications so it may all be psychological), so it's either Y or J on those airlines.

I refuse to fly BA WT, but since WT+ works for me then BA is still in the running when there are no good J fares.