I haven't heard much personally. I've seen a couple of bug reports regarding crashes. One person says they're using the "latest" Armory but hasn't confirmed which exact version they're using (i.e., I don't know if they're using a patched version). Another person was using 0.91.99.8 and said that upgrading to 0.91.99.11 fixed their particular crash issues. Again, I'm not promising anyone any magic bullets, but anecdotal evidence seems to suggest that the OS X build is reasonably stable at this point.