I do combine SU with other CAD programs.
The main reason is that I am lighting designer and exact lighting calcultions can not be made in SU.
SU is the pre- and post processor in my workflow.
The structural model of the lighting model is created is SU.
In 99% of the cases the architectual model is too complex for any lighting design program. This simplified model is imported into the lighting design software.
After the actual lighting design is made the luminaire’s 3D represantion is imported into SU.
Anyway Layout was always a misery for me.