Interesting test even though I must admit it hasn't had my fullest attention due to the Olympics.
SA were right to declare when they did and England were right to bring KP out first to try for the result. Sadly his early wicket set the tone and when Prior went in a moment of madness it was all over.
Perhaps England would have been better to not only bring KP up the order, but also promote other players too. Maybe open with KP and Cook, followed by Prior, Taylor, Bell, Strauss, Trott, Bres etc. If you are going to attack hard for the result it seems a waste just to bring KP out early when there are other very good T20/ODI players in the squad.
Sadly the big story from this test is that it could well be KP's last outing in an England shirt. It really is shocking how both sides have allowed this to happen. While the ECB are certainly not blameless, they really need to sort this out. In cricket KP is a superstar and if rules need to be bent (or easily rewritten) to appease him to some extent then so be it. In particular the IPL is not going away and is an easy way for cricketers to make a few quid. All the ECB can do is not book a series for those dates. If you do book a series and a player that has given good service to the side over many years wants to skip it to play IPL, let them.