BA has a new lounge at JNB and it is quite good, although not in my top 5 list.

number_6 sometimes lounges do come into play. For example flying from PER to AKL on QF I have a choice of transitting at MEL, SYD or BNE. While schedule, a/c type, ease (or lack of ease) of changing terminals are factors, so too is the vast difference in lounge quality (BNE much much worse than MEL and SYD). Similarly between UK and Australia the choice of transitting via SIN, BKK, HKG, NRT, LAX and SFO can be influenced by lounges, although I personally have more important considerations (like avoiding the horrid US transits where possible).