hi,
Not much changes really, apart from less portable features, cause they messed up the axis to begin with and now it's obviously showing as they provided a 2d version of their 3d world. But that's not too bad I guess.
the main different is a dedicated 2d physics engine and some work done for graphics management. But in all honesty ( else I would need hard evidence with profiling results) , doing it old school works just as good, combined with the regular 2d assets like 2d toolkit, ngui, and the likes.
bye,
Jean