Now halfway through my SA trip, figured I would update with what I've learned/seen so far. This info is primarily for others who do not visit SA often and/or are primarily non-SAA flyers.
Checkin: Evening flight (2130) from LHR-JNB. As 1k on UA (thus *-gold) I was allowed to use the business check in line. These lines were not particularly long, only about 6 people/families checking in at two counters when I arrived. However, 4 of these groups took an extra-long time to process -- I got the impression that these were people who had lots of money (hence paid biz class) and were NOT frequent fliers: many of them had no clue about what you could/could not check for bags, what you could(not) carry on, where the gates where, etc. Not unpleasant, just an observation. The checkin staff at LHR were polite and professional, as expected.
Lounges: I was given a pass to the LHR SAA lounge, which I thought was very nice -- it compares most favorably to the ugly UA lounge in Terminal 3, and on par with the SAS lounge which I've also used. I was told by the checkin staff that my *A status would get me into the arrivals lounge in JNB, where I needed to wait about 3 hours for my wife to arrive on the flight from the USA. Unfortuneately, when I got to JNB I was politely but firmly denied access to the Voyager lounge in the Intl. terminal. I don't know who was wrong, the checkin staff at LHR or the desk agent in JNB, but I was not particularly pleased to be denied the peace, quiet and shower I'd been promised earlier.
The flight: boarding and departure were slightly delayed (maybe 30 min). No announcement of the delays were made in the SAA lounge, nor were announcements made that boarding had begun, even though I was told they would be when I entered. Seat 81k: window seat on the upper deck of a 744. I found the full-sided seats to be rather narrow and uncomfortable, although the legroom was very reasonable. IFE was modern and worked OK for what little time I spent with it. Skipped dinner (had just eaten at LHR). Cabin crew were polite and professional, nothing exceptional but absolutely nothing to complain about either.
No problems with JNB baggage or immigration, although the wait for immigration was quite long (probably 45 minutes). Baggage was waiting unmolested when I cleared immigration, breezed out through customs.
JNB airport: JNB Intl terminal was very busy, lots of taxi and porter hawkers (signs everywhere remind people to avoid these). As above could not get into the SAA lounge, so I camped out upstairs near the food court and connected via wireless and waited for the flight from the US to arrive. Walk to the rental cars is about 5 minutes, had no problems getting the car or getting out of the airport area. Airport area felt perfectly safe, though you're well advised to keep yor bags close.
This week will include a return flight to Cape Town (via the domestic terminal) as well as the JNB-DKR-IAD run. Will post more after that happens...