I recently updated to OS X El Capitan (I skipped Yosemite altogether). In doing this update I can honestly say my computer has gotten worse. No apps were broken. And I didn't encounter a lot of bugs. But here is the main issue:
My Mac is now really slow.
It is sluggish all around. But the biggest thing is that Spotlight went from being super fast to super slow. And I am a huge Spotlight user.
At the same time, the new features of the OS haven't brought any benefits.
I don't use any of the new Cloud features of Apple. I mostly use Google and Amazon cloud services. I use very few of the native built-in Mac apps either. For example, I use Chrome. Not Safari. I use gmail. Not Apple Mail. And so on.
Upgrading to El Capitan just made my Mac worse.