Using only Darwin instead of Linux or FreeBSD was never really attractive. Contributing upstream is difficult to impossible, since Apple was never set up to take your contributions. The different Darwin distributions never really developed a direction or a unique feature set.
The only feature that sets Darwin apart from FreeBSD is launchd instead of init. The rest is mostly downsides like a weird file system. You can get dtrace on many other OSs today too.
The only feature that sets Darwin apart from FreeBSD is launchd instead of init. The rest is mostly downsides like a weird file system. You can get dtrace on many other OSs today too.