I carry both an A9 (for reading books, newspapers, magazines, browsing) and iPhone (for music, calls, banking, audiobooks, camera). I actively use the A9 screen about 10 times as much as the iPhone and love it.
I'm running Lineage on it, and use EasyScroll so I'm not limited to supporting apps for page turn via buttons.
I don't use it as my sole device because the iPhone integrates so well with my Apple Watch, HomePods, AirPods, Mac.
The DC dimming on the Hisense front lighting is much better than some other e-ink devices (I assume some use PWM - the lighting on recent Boox devices gives me an instant headache).
Also the lighting can dim very low for comfortable reading in the dark. I use macrodroid to easily switch between different low light settings.