Well, it's significantly easier to implement than a octree. Game is actually 3D under the hood, projected at a careful angle to look isometric 2D.

The reason the game is 3D has to do with partially visible things being way easier than with isometric textures layered in the right order.

Also, now that i just grab a pixel back from the GPU, it's no overhead at all (to construct or get the data for it).