As for backwards compatibility, all I know at the moment is my spawn code is maintaining what I had before the transition but will not allow me to spawn more/additional creeps until i change my code over.
So my rooms are at their "stable position" that ive had them at for a few days, but if i want to create a builder, it won't do it because hey, new code stuff now. xD
I'll have to try and convert this stuff later today.