I recently upgraded from Yosemite to El Capitan but I couldn't get the Split View functionality to work.
For people who don't know, the Split View lets you run two apps side by side.
Get Split View Working
To get it working, just go to "System Preferences" -> "Mission Control" and check the "Displays have separate Spaces". You'll have to logout and log back in for it to work.
Now you'll be able to run two apps side by side. Enjoy the extra bit of productivity, or use it to watch YouTube videos. I won't judge.