Putting this here because there are hardware and software components that will be impacted. SONAR may be PC-based, but I know some of you have Macs.
 
From NI's email
-------------------------------------------------------------------------------------------------------------------
 
CRITICAL compatibility warning with the upcoming Mac OS X 10.11 El Capitan upgrade

Dear John,

Before upgrading to the latest version of Mac OS X – version 10.11 El Capitan, please consider these potentially serious issues concerning your KOMPLETE, TRAKTOR, and MASCHINE products. Two major issues have been identified:

1. NI plug-ins do not pass the AUDIO UNITS validation in Mac OS X 10.11 – Logic Pro affected
In Mac OS X 10.11, Native Instruments AUDIO UNITS plug-ins will not pass the AU validation and will therefore not be available in Logic Pro. The root cause of this issue has been identified and a solution is currently being developed in close contact with Apple.

2. Incompatibility with some older NI hardware
There are compatibility issues between some older NI devices and Apple’s upcoming operating system. This issue triggers a 'kernel panic' – this serious problem will crash the connected computer immediately, resulting in loss of any unsaved work, or serious disruption of a performance.

The following hardware is affected:

TRAKTOR KONTROL S4 (MK1)

TRAKTOR KONTROL X1 (MK1)

TRAKTOR AUDIO 2 (MK1)

AUDIO 8 DJ

AUDIO 4 DJ

AUDIO 2 DJ

MASCHINE (MK1)

GUITAR RIG 3 (RIG KONTROL 3 hardware)There are beta drivers already available that fix this issue. Updated drivers will be released as soon as they have been fully tested on OS X 10.11 – shortly after Apple releases OS X 10.11 to the public.

Download the beta drivers here

To keep your system working normally with the affected products, we strongly recommend waiting before upgrading your computer to OS X 10.11 El Capitan until these issues have been fully solved by either Native Instruments or Apple.

Stay up to date on all future developments regarding Mac OS X 10.11 compatibility here

Thank you for your attention,

The Native Instruments team

 Although I don't have a Mac, I do have Maschine Mikro MK2....yet unaffected by this update.
A lot of Win users are still having problems with Maschine's latest update that seems to crash Sonar.
 
It's good t know what's happening in the pipeline....thanks John for posting this.

Best option - do not upgrade to El Capitan, or Yosemite for that matter. 
Tim Cooks ruined OSX when he took over for Jobs.
 
The gap between Windows and OSX is closing fast - and recently, it's not been because Microsoft borrowed ideas from Apple or implemented features similar to OSX but because Cooks trashed things which made Mac OS what it was. 
 
I think I've cursed Cooks more often in the last 6 or 8 months than I'd cursed Bill Gates in my 10 years on Windows...

LOL Speak of the devil... Look what just showed up in my newsfeed.
 
http://www.macworld.com/article/2987066/business-software/tim-cook-on-apple-and-microsoft-partnership-its-what-customers-want.html
 
Ironically, the strength of Apple was that it basically never listened to "what customers want". Instead, they relied on a strong sense of direction, with very little compromise, which maintained a sense of coherence and a very well-integrated environment.
 
Putting this guy in charge is like asking Pamela Anderson to pick up where Albert Einstein has left...

Rain
... 
Putting this guy in charge is like asking Pamela Anderson to pick up where Albert Einstein has left...

Even better ... the movie "Insignificance" by Nicholas Roeg. At least it tries to makes sense of something instead of ignoring the reality ... that the people that end up using these things, need them to work! I just find it pathetic that the media does not nail those companies for their lack of respect for people ... the very folks that pay their wages!
 
Cooks is right of course, but the days when Mac and Windows were different, are long gone ... the MAC's are no longer the specialists in graphics and music like they were for many years, when Microsoft was too busy trying to sell the Office and Microsoft Word ... and Apple has always been lax on software, not to mention that its prices were prohibitive and ridiculous.
 
Tangerine Dream even talks about some of their tours with like 10 MacIntoshes strung up together and a couple others for backups! It will be fun to see the biography/autobiography from Edgar Froese, just to catch on a lot of those juicy bits and how they made it work. Nowadays, you can see Jordan Rudess play a hand thing, and you don't even think twice ... about if it is a Mac or Windows.

Moshkito
Tangerine Dream even talks about some of their tours with like 10 MacIntoshes strung up together and a couple others for backups! It will be fun to see the biography/autobiography from Edgar Froese, just to catch on a lot of those juicy bits and how they made it work. Nowadays, you can see Jordan Rudess play a hand thing, and you don't even think twice ... about if it is a Mac or Windows.

Huge fan of T.D. It was really sad to lose Edgar last January. It'll have to be a bio, unfortunately.

I still see Mac computers everywhere in major productions and most recording studios. None of them are running any of the newest, latest OS though.
 
While it is still manageable, what worries me and many other Mac users I speak with is that trend that we see since Cook is in charge. 
 
When I got my first Android phone a few weeks ago, it provided me with an opportunity to reacquaint myself with life outside the Apple sandbox. And there are great things to be said about it. Nevertheless, for me at least, as of right Apple has not yet crossed that threshold where the alternative will be preferable. Not yet, because, the way things are going, I don't see how we won't go past that tipping point in a relatively near future.
 
On the other hand, there's Logic X. That's one thing Apple didn't screw up - even though I can't claim that X is yet as solid as 9 was. But 9 was just phenomenal - the best piece of software I've worked with in terms of stability. Still, X is a workhorse and Apple recently spoiled us by throwing in what was my favorite 3rd party synth before they acquired it, Alchemy. 
 
I don't see myself moving away from Logic anytime soon. Though these days, I wish I had an old PC running XP and Sonar 8.5 to mess with old projects... :P

TheMaartian
Huge fan of T.D. It was really sad to lose Edgar last January. It'll have to be a bio, unfortunately.

The book was not finished, and Bianca is trying to put the rest of the touches in it. I think she will also slim down the bad stuff with Christopher Franke, but we won't see that until it gets published.
 
It was due "in the fall", so we should be closer to it than not, but the whole TD thing right now, is getting too messy for my tastes and I am not sure they know which way the earth revolves around Jupiter or Saturn. And no communication, which is worse. I am not sure that Bianca has the ability to finish the book, and the folks left behind are (supposedly) working on some material that was left behind, and honestly, I am not feeling it ... and Jerome said he wouldn't get anywhere near it. Jerome is too song oriented for my tastes, but TD had become theme oriented in the past 20 years ... and anything knew will probably try to bring back some of the old sound experiments to the music, and I'm not sure that they have the aesthetics to make it work.