I've taken Delta twice, SAA twice, Qatar once, Ethiopian once and United this last time (although, the JNB leg was Lufthansa).
I will avoid United in the future unless they start showing a track record of actually maintaining flight schedules.
Qatar makes the trip longer, but it's a really great airline.
Ethiopian was fine except for the short layovers in Addis Ababa. I hope they are working on their process for dealing with firearms.
I'm going to look at Lufthansa more closely. They dealt with the unscheduled arrival of firearms very well and FRA is a nice airport.
This last trip really hammered home the need to use a travel agent. Travel Express dealt with the issues in a highly efficient manner.