Mixed feelings.
On the one hand, they never truly went all-in. No iPad ever had it. Several iPhones never had it. Given how otherwise similar using iOS is, that put a significant dent into making 3D Touch easy to explain. "OK, if you press like this, you get additional options… unless your device doesn't support it, in which case you have to do an entirely different dance."
They also never quite figured out the UI. Why is deep-pressing an icon a different thing than long-pressing, but only sometimes? In Control Center, with 3D Touch, I deep-press to get more options, but on devices without it, I long-press (for no reason whatsoever, I can't long-press if the device does have 3D Touch). But on the Home screen, the same doesn't apply; 3D Touch shows the widget and various shortcuts, whereas a long touch enables wiggle mode. Similarly, in Tweetbot, long-pressing shows a share sheet (why?) but deep-pressing shows peek/pop.
They've had three major releases since the debut to unify this.
On the other hand, peek and pop is actually really nice UI to have a glance at stuff. 3D Touch as a shortcut to faster long-presses also works well. Deep-pressing the keyboard feels more right than tapping and holding the space bar.