I am wondering what the real difference will be in day to day use? Other than the "south" line in installed apps, it sounds like it will be very similar.
As I understand it, the new migrations module is more fully featured than south: eg, it intelligently squashes/flattens migrations together to avoid redundancy when you run the migrations (say you create a model in migration 1, and remove it in migration 3 after changing approach, the whole operation will be skipped).[0] This will speed things up if you have a lot of migrations to run.
I think I heard that some of this stuff will be backported to South for those of us stuck on 1.5/1.6, however.