I see this akin to in-car DVD players vs ipads. There's a permanence and durability trade-off, plus the part that irks me a little, which is shifting the burden to the customer (SWA, who I love, has done DIY streaming for many years and I never mind it, but those are normally sub-3-hour flights. And yes, I still miss in-flight magazines.)
If they could push everything to your device that a seatback screen would have (including flight graphics, etc), then I'd be on board.
In a way, it's a little refreshing to see airlines do what carmakers refuse to do -- admit that our devices are usually better and newer than anything they could offer us 🙂
Plus maybe then, the screen won't freeze on some naked violence while the announcements are being made. The kid in the seat next to me just stares....