My frustrations with the Archicad model exported into SU are mainly when it comes to trying to work with one level (story) at a time. Maybe it is the way the Archicad file you are working on is set up? The Archicad model isn’t set up they way I would set up a SU model necessarily. Do you have layers set up by story that you can turn on and off? When I get the model into SU, the walls, for example, are all on and I have to try to make section cuts work to then work on them more (add furniture, wallpaper, wall finishes, etc) and it get really cumbersome. The other, more minor things is the the extra lines on faces (between faces) that archicad brings in.