This is such a hard question to answer. On the one hand, crime is a real problem in South African. On the other hand, I think a lot of stories get blown out of proportion and we often let our fears get the best of us.

One little interesting anecdote - I attended a Brai (barbeque) in a township in Paarl. Afterwards, we went on a drive through of the surrounding townships. One was named Chicago. So named, according to our host, because of Chicago's reputation for high-crime.

That being said, I woudn't necessarily worry about traveling there. Still, just be on the alert and remain more aware of your surroundings in South Africa then you might be elsewhere.

Speaking from my own experience, I had no problems- both in Capetown and Jo'burg. Bu there are definitely areas (particularly in Jo'burg) which are no-gos. Lonely Planet/Rough Guide discusses this. You also would not want to go into the townships alone or without someone who lives there and knows where they are going. There are tours of some of the townships - I assume those are ok.