Just a nitpick, but the two changes referenced in the parent comment (whole screen 'cards' for multitasking view and using gestures for such) are straight from WebOS for both Apple and Android. Being a step back in UI is also a bit subjective, I personally find it a lot easier to navigate between the apps I regularly use now.

Edit: Just installed the android Q beta and the back button is still present, I was not aware of the potential loss of the back button. I can see why that would be considered such a step back in usability.