With the new SDK, I don't see any way it will be possible to avoid stuttering if you're using a mirror texture. The examples demonstrate using the mirror FBO by disabling v-sync on the non-Rift display device, so that buffer swapping doesn't trigger a delay in rendering the next frame for the Rift. But on OSX platforms, V-Sync isn't user selectable.
Is this a known issue or is there a working solution?