Unfortunately Apple is trading usability, readability and stability for eye candy & toys, with the aspiration of entrenching the user ever deeper into Apple`s diverged ecosystem (iPhone, iPad, Mac). I have applied multiple clean installs of 10.11 only to incur multiple issues, that result directly in forcing the need to reload 10.10.5; Mail, Preview, Airdrop, Wi-Fi to name a few. The OS X point updates have either fixed, introduced new issues or done nothing.
I get to a point with 10.11 with the core applications not functioning correctly, that there is little point to proceed further with the system, adding more complexity and third party applications is simply wasting my time. For many the story was the same with 10.10 personally I had no major issues, although I don't care for the reduced readability of the OS due to poor choice of font and flattening of the OS in general.
I have always used OS X as it was a super stable platform for productivity, these days not so much, with the focus being ever further on casual use, and social media. For 2016 I am seriously looking to move all business related systems to Windows. I don't need a desktop OS that is trying to imitate and keep pace with mobile platforms, delivering little tangible improvements in productivity, that may or may not work as intended with each new revision.
My own opinion is; OS X is steadily degrading into little more than a vehicle for an entertainment & social media platform. OS X revisions are released needlessly rapidly, rushed and incomplete. Launched with much hype & hubris, however delivering little if any real tangible value for those productivity focused, this serves to do little more than degrade the value. Point updates are focused on fixes that should have never been required, due to the initial hasty release, that may or may not be fully functional by the end of it`s short cycle, in short a vicious circle.
It would also appear that others have similar opinion, nor are these haters, more serious users with genuine concern;
http://www.marco.org/2015/01/04/apple-lost-functional-high-ground
http://macperformanceguide.com/topics/topic-AppleCoreRot.html
http://www.macobserver.com/tmo/article/mac-experts-weigh-in-os-x-quality-is-declining
Same hardware runs 10.10.5 flawlessly...
Q-6