I've not done it, but am planning to do the south to north route at some point! I've travelled a bit in E Africa, so shall share what I know...
Kenya, Uganda and Rwanda are great for travelling in - the majority of the area in these countries is safe, just check the local advice on the FCO website. For example avoid the far NW of Uganda, and the borders between Rwanda and DRC or Burundi.
As for some of the others - i would avoid if possible Central African Republic as it's pretty unstable, also DR Congo on the eastern side is best avoided due to fighting, rebels etc. Also Chad and Sudan I'd probably give a miss...if I were going to try and do it, I'd probably travel South, go across the very western part of DR Congo, then travel round Congo in Angola (apparently its a lot more stable than it used to be), then through Zambia, Tanzania, Rwanda, Uganda and Kenya (or could just miss Rwanda, Uganda and Kenya and go for the coast in Tanzania). Its a pretty big detour, but if you read up on the security situation in each of the countries you have listed on the FCO website, you might agree with me!
http://www.fco.gov.uk/en/travelling-and-…