Flown the DL 767 J cabin a couple of times for long haul flights between PVG and SEA, and from ATL to SCL. I honestly thought it was alright especially if you want to sleep since it was lie flat. The only bad part is the small cubby hole for the feet so your feet will definitely touch the side panels. Think of it like sleeping in a sleeping bag during camping. I did like Delta's large pillows and duvet though so always had no problem sleeping as I do not really move much. I also do not sleep sideways if that is a consideration.

AF new J is definitely a step up but not sure if it is worth an extra 2 hours of the time. I have never tried this product before though it should be similar to CX long haul J, which is very good!