I have never had problems with internet check-in, not with VS, BA, SK, IB, or TP. I check in, I arrive at the airport, I present my ID, bag is weighed, labelled and it's all over and done. Perhaps the thread should be changed to "KLM online checkin is ********".
cavortingcheetah, what you experience at JNB is not a failure of online check-in, but rather a security check against the pax list. It's designed to prevent illegals getting anywhere near airside (although it's probably easier to bribe a gate guard and get airside that way). Considering that SAA has most of the check-in spaces, and VS and others have to make do with 4 or 5 desks (Tuesday only had 3), it's managing the crowds. I had no problems checking myself in online, proceeding past the initial pax check, and getting the bag dealt with.
JNB has improved in the last year. The new international departures area (landside) feels a lot better than before. There is a lot less people crush than before.
S.