Check out this great page that has a variety of maps to show the differences between northern and southern Sudan. We need to be careful to consider how much of this is given by geography and how much of the differences are driven by politics (which may or may not be driven by geography). The oil and the basic topography are essentially given by history/nature. The distribution of ethnic groups largely precedes independence as far as I remember. But infant mortality, water/sanitation, education, and food insecurity are certainly the products of politics. The series of governments dominated by northern Sudanese invested in the north and not in the south. Which is why the referendum will be decisively for independence. Does not take an expert on secession to guess that.
here. Given the experience of Macedonia, I would recommend against using any name that includes Sudan prominently and be careful of using Nile since the Egyptians might be sensitive. Of course, the name that will arise will be mostly driven by domestic politics, and I have no clue how the disparate groups (see this pic from the bbc site linked at the top) will come to find a common identity. This is one of the big challenges ahead, as the key force thus far united the people of the South has been the nastiness of Sudan's governments. Once that is gone, I am not sure what will be the glue that keeps the people of southern Sudan together.
Given that this has been a process sanctioned by multiple international organizations, the new state should gain recognition fairly easily. If the north lets southern Sudan go, then even Arab states will probably not mind. If the north reneges (and this would not be the first time), then I would expect ethnic ties to kick in so that countries where Arabs/Muslims are important constituents will support the north, countries with blacks and non-Muslims (especially those with a history of bad relations with Arabs/Muslims) will side with the South. And China will side with whichever side can most credibly guarantee oil and other minerals.
Either way, Darfur is screwed.