The Houdini 15.0.277 build contains a fix for AMD GPUs on OSX which restores stability for this platform. At the recommendation of AMD, this requires multisampling to be disabled until a driver bug involving depth multisampling can be fixed (possibly 10.10.2?). Once the driver fix is done I'll put a version check in to only disable multisampling on affected OSX versions (graphics drivers are tied to OSX OS versions).
The result of this fix is that Houdini on OSX/AMD platforms will now use dithering instead of ghosting for ghosted objects and Wireframe Ghost display modes, and it will of course lose full-scene antialiasing.
If you were experiencing stability or image quality issues with AMD GPUs on OSX, please upgrade to build 277.
This only affects OSX with AMD GPUs; all other platforms are unaffected by this fix.