Apple released Mac OS X Mavericks (10.9) yesterday as a free upgrade. Please find our compatibility notes, upgrade checklist and other useful information in this ArchiCAD Wiki article: http://archicadwiki.com/OsxMavericks
Switching to perspective or axon will crash AC in OpenGL but will not crash in Internal engine. There has been a case opened on the issue with GS. I spent over 10 hours trying to troubleshoot it with no luck. Also, there is a very slow response on reading from the Finder for files from Mail and AC. Other than that there are several great improvement and it is quite a bit faster.