Today's #IfcOpenShell commit writes docs about the binary tree feature. Creating a geometry tree allows you to quickly filter objects by coordinates and bounding boxes.
This feature is useful for doing any type of geometric analysis. For example, what pipes are going through an opening and therefore what fire rating should they have? Or select a subset of objects in a 3D bounding box in a large building.
What this means is that if you do collision detection between two models, you get nice image previews where two objects intersect. This is critical when architects and engineers coordinate designs. Pipes shouldn't go through beams!