I picked up a Gen4 ATV lat week and am having mixed feelings about it.
I have a Mac Mini running Kodi to playback video from a NAS.
I grabbed an ATV3 last year to plan Netflix and Hulu.
FTA TV was handled through the TV's built in tuner on the off chance we actually watch FTA, although I do have a 1TB PVR in a cupboard I occasionally think about hooking back up for recording the news.
Everything is routed through a Yamaha Receiver to a Samsung TV.
Everything is controlled through a Logitech Harmony One remote.
The Mac Mini does a couple of background tasks too; Central iTunes Music Server (played to AirPlay Speakers around the house) and OSX Server to caching updates. It used to also do AirPlay (before the ATV3). The caching isn't really needed anymore (I'm now on a high speed connection) and I could load iTunes is largely replaced by direct streaming through Pandora (or I could load iTunes onto my NAS).
The ATV4 replaces the ATV3 completely PLUS with Plex and/or MrMC it does the video playback from NAS too.
1st up, the remote. It's a huge step forward from the old remotes, Siri integration is great... but since I have a Logitech remote it means I need to have a second remote to use any of the advanced features. I think it will also need a little tweaking (or re-learning on my part) before I'm comfortable with how the Harmony will work with the ATV4. Within apps it behaves differently to what I am used to.
Since I have a receiver AND TV I don't know that I can have everything turn on/off with the ATV automagically, but something to look into one day.
Similar to the old ATV3 Netflix, Hulu and Apple purchases work brilliantly (although I'm struggling with how different Netflix is now vs the old version, but I'm sure I'll get used to it).
Plex... well Plex works very well with a but. As much as I try to love it, it's always a little clunky for me. Fast Forward/Rewind currently has lots of issues, but saying "skip forward 5 minutes" or "skip to 1 hour 23 minutes" works** (In theory). I'm also finding everything is transcoding and while I have a fast enough server behind it, it still sucks if you try and skip forward / back it lags out and doesn't always come back.
It's a new app on this platform and it will get batter... but we will see. (Essentially it needs it's only video player rather than replying on the Apple built in one that requires everything to be transcoded).
It's Kodi for ATV4. It works brilliantly, just like it did on the OSX before. The limitations are no plugins... so no skins that the family are used to and no extra little plugins that we are used to. That said it seems very stable for me and no one has complained significantly a week in.
I have sort of replaced like with like but with compromises. Sure I theoretically have less power draw and have to switch between less stuff, but it's change for change sake. Everything was working anyway.
As a second unit on a bedroom TV (which I don't have) it would be awesome. A single box that brings me everything I want with a single remote. Great.
But for me, I'm trying very hard not to pack it back into it's box and sell it on the only thing I will be missing is the Siri integration.