I've had 3 long-haul flights on IB in the past month, but all in F. Very good in F, for J I would say slightly better than WT+; definitely not worse, but also not anywhere close to NCW. So if you are choosing WT+ and IB J for same price I think IB J is a reasonable choice if the flight schedule is acceptable (to JNB it should be). The airplane safety, cleanliness and maintenance seemed quite good and the pilots were also good, similar to BA from what I could tell. IB still has awful ground handling so don't expect much help with ticketing or baggage problems though.