At Rill Architects we run ArchiCAD on Mac OS X. If you work at Rill, this is your stuff. If you don't, but you work in ArchiCAD, you may find something interesting. Anybody else, I don't know.
Location: 13 Special Construction. This is so cool. Using Solid Elements Operations and this object, you can cleanly slope the top of a curving wall. Handy for landscaping.