My two cents on Garang.
My personal opinion is that there probably was not much foul play involved in Garang's death, the weather was bad an his helicopter had already aborted one landing due to the conditions. If there was any foul play involved (which is certainly a possibility) I would guess that the Sudanese Government had nothin to do with it. I have a lot of issues with President Omar al-Bashir, but I don't think he would be stupid enough to whack a strategic partner whose help he needed to hold the country together. However, there are plenty of people who could benefit from an unstable Sudanese Government: Islamic militants who would prefer that Muslims keep their dominance in the government, rebel groups in Darfur who would prefer that the government be distracted, or rogue elements in Southern Sudan who would prefer to secede rather than unite with the government. However, I will reiterate that it was probably bad weather that brought down Garang's helicopter.
However, what actually happened is not quite as important as what people perceive to have happened. The violence has already started in Khartoum and Southern Sudan due to the fact that Southern Sudanese tend not to trust the government which has oppressed them for so long. I really don't blame them for thinking that al-Bashir had Garang executed, that would have been a distinct possibility if this had happened before the peace agreement. Whether Garang was murdered or not is immaterial, what matters is that he is now seen as a martyr for the cause of Southern Sudan. If anyone wanted to destabilize the fragile peace, they have almost certainly succeeded.
Dr. John Garang