the export from AC7 to Universe works nicely, but I always process the files trough Transporter before importing them in Universe. This allows to get rid of the default AC camera and AC sun that are always exported from AC, plus killing all the links to AC textures.
Note that Transporter is currently being ported to OSX and Win, recieved the latest beta this morning and it works perfectly now, so the wait shouldn't be much longer.
The export from AC8 to Universe works too, but there's a couple of bugs that GS is supposedly in the process of fixing, fingers crossed.
As for Radiosity in Universe 5, I do use it for interior renders even though it's still quite unpredictable and tricky to set up. The current version 1.03 is very stable and has progressed quite a bit from the previous one. Keep in mind it's still under development and can only improve in the future. Now it can easily process 100-200k polys scenes, which allows for a lot of details in an interior model.
I also use ArchiCAD and Electric Image Universe. However, I'm having difficulties exporting FACT files form ArchiCAD 8.1. Does this work? My exported models won't show the polygons in Transporter. DXF export works, but I prefer to stick to FACT files.
Also my scale is way off. I have done this in the past with ArchiCAD 7. Did something change/break? Or have I gone mad?