Performance?

Good point about the minimum bounding rectangles. Thinking about it some more, I suspect that the RS speed of a kd-tree that uses minimum bounding rectangles, would be extremely similar to that of a R-tree really. Sure, the partitioning is a bit different but both have reasonable enough partitioning and with the minimum bounding rectangles the search algorithm would basically be the same.

Yeah, that rebalancing aspect is what prompted me to do some r-tree experiments in the past.