I did what you are proposing OP. Swapped a WDTV for an Apple TV.

At first I had plex running on the ATV (and it works really well), then I was allowed to replace the TV, and the new TV can run Plex, so I now do that from there. I use the ATV for Netflix and Hulu.

All very Wife Friendly (especially using a Harmony), and the GUIs are pretty slick.