The Southern Sudan Centre for Census, Statistics and Evaluation (SSCCSE) officially launched the Census from the South today. The Chairperson of the Centre, H.E. Isaiah Chol Aruai endorsed the results. The information will hopefully be useful for planning purposes.
The Census was actually carried out in 2 halves, the Southern part entirely by the SSCCSE, and the Northern part by the Central Bureau of Statistics (CBS). The Southern part is likely to be more reliable. The Centre has declared that external agencies are free to audit the archives and documentation, and the whole process has been very open. The North on the other hand, has not even shared their raw data with the South.
This is why the main SPLM gripes seem to be with the Northern data - the main issues being the under-counting of the Southerners living in the North, and the over-counting of Darfuris.
The results are available on the website of the Northern Central Bureau of Statistics, and will hopefully be on the SSCCSE site before too long.