I'm very impressed with South Africa's performance in the ODI series and their complete obliteration of England's plans (so far, at least). Apart from that, I am also happy that English cricket realizes that all their Ashes build-up was a wee bit inflated if a team like South Africa can take them to the cleaners. England are better in the longer version of the game but if South AFrica go on to take the series 5-1, I think their confidence will have taken a bashing (in both forms).
That said, South Africa have shown themselves to be one of the top 3 ODI teams in the game, in my opinion. What they really lack is the bowlers. Apart from Pollock, if they can get one or two more match-winning bowlers, they would be the closest to the Aussies. They've got great batsmen and a long batting order. And they've got Kemp who looks like he can hit everyone for six.