Split screen multitasking in iOS 9 was my favorite new feature Apple introduced last year, so I was happy to see Android catch up this year and add split screen as well. As is the Android way though, this feature is only really half-baked in this first incarnation.
You first get tipped off when many apps display a warning telling you that this app may not work in split screen (every time you launch the app). It's made worse when you realize that many apps will display in split screen, but they will not update their status unless they are the "in focus" app on screen. This is shown in the video above, and I can imagine would be incredibly frustrating.
This is a very Google-y way to add a new feature, as all of your apps "just work" without needing to add any code, but the bar for "just works" is incredibly low. Yes, pretty much all apps will display in split screen, but only one can be focused at once. The fact that you can get a notification that you received a text message, but see no update in your messages app on the right of your screen until you bring that window back "in focus" would be maddening.
Ultimately you either love this because Google is giving you more options, even if it breaks a few things, or you don't like it because you prefer Apple's approach of only letting apps work with split screen if they explicitly build in support.