"microkernels" I agree that it should be possible to upgrade the backend without having to upgrade the frontend (so to speak) of the OSes. In my experience, t

"microkernels" I agree that it should be possible to upgrade the backend without having to upgrade the frontend (so to speak) of the OSes. In my experience, though, even the backend for OS X is massively changing. Networking, in particular, seems to be changing every release.