It'd be nice to be able to snap into real blocks at 90 degrees rotations. This would allow people to do things like rotate something like a room...to get a new view. XD

Indeed. It will be a little tricky to handle rotations around x and z- as minecraft itself does not support vertical rotation of blockstates by itself. Take Furnaces for example, since it cannot face up or down it's unclear how it will end up when rotated that way.
I think once vertical slabs and stairs have been added to the Mod, we might be able to simulate the rotation well enough.