Ive used various mac/windows based music platforms over the years since around 1997 and still think Mac is the better platform for audio. Heres why: 1) ios/osx has a baked in low latency audio framework in Core Audio which means even on board audio can run at < 10ms round trip latency 2) Logic is still the most solid DAW Ive ever used 3) Windows has yet to offer a compelling Audio experience with out serious hardware.
I will agree that the new mac pro was a big step backwards from the previous version. I had an 8 core mac pro from 2008 and that was the perfect music pc. Im sure the new one is fine, but I dont care about the aesthetics of the computer as long as I can depend on it to record a session and not fail.
The Native Instruments issues dont really surprise me and in my experience with that company their software quality ranges from buggy to mediocre (Komplete 1-8) to the point were I could not find a compelling reason to continue using their software. I could certainly understand a company acting defensive and blaming the OS manufacturer when they are flooded with bug reports.
To that I would also offer a counterpoints of Propellerheads Reason. Their software is consistently bug free and solid performing. So it does not seem to really be a "Mac" problem. I currently use a universal audio apollo 8 and that also performs solidly via the lightning interface at near real time latency. Point being, its possible to make solid software for mac.
Anyway, I don't think that the mac is perfect for audio, and the situation may be worse for video, it sounds like the new mac pro is a dud for pro users, which is disappointing.