as for the v2015 sp3 release:
- the spaces assignment happens for the exterior outlines of the building parts, the existing spaces get no more duplicated.
as i have for each storey a few significant design layers (slab, spaces, walls and 3d_parts for elements i don't want to be visible on the 2d floor plans), the new (exterior) spaces get created on the slab layers. to be frank i don't understand it, but there must be a method. some minor space creations happen on the roof for the mechanical ventilation chimneys' exterior outlines, but it's no comparison with the chaos of previous releases.
- the gbxml export renders ok, no crash, the file size 4.2 mb, exported from the 208 mb project file. to compare: the ifc export is some 84 mb.
- the (same) gbxml file imported into openstudio (v 1.5.3.) winds up in an error (the error report included).
all in all, the gbxml export procedure is more smooth, but fails nevertheless at the gate of another bim evaluation software.
more to come...
rob