Ashley
When using tile based levels I often use an array to define obstacles, so it would be handy to easily import the preexisting array instead of generate it again.
It would also make easier to define our own generation map algorithms without depending on objects placed on the layout.
It's a speculation from my part, but I guess that the algorithm to calculate the obstacle map from polygonal, unaligned, rotated objects, that tracks partially covered cells, can be a lot more costly than manipulating the array directly. So maybe it's possible to have a world that updates much more frequently without impacting so much on performance.
Anyway, an integrated way to communicate with the array object would be useful. Of course if direct cell manipulation is added you can iterate through the array and update every cell like SketchyLogic said, but an JSON load would be pretty handy.