On Saturday South Sudan was welcomed as the 193rd country at the United Nations. It is not semi-presidential! In fact, the interim constitution, which is available here, is resolutely presidential.
The president is directly elected. There is a vice-president, but no PM. There are no mechanisms for parliament bringing down the government. So, this is about as presidential a constitution as you can get. Given South Sudan faces a difficult post-independence period, let’s hope that it will be a successful case of presidentialism.
Sudan Tribune reports that the interim constitution was finally passed only a couple of days before independence and it is possible that amendments were made to the document that I link to above. Apparently, a permanent constitution (if that is not a contradiction in terms) will be drawn up in the next period.