We actually made a decision a couple weeks ago to give a Mac mini running Plex a whirl again. I had a few issues the last time I gave this a whirl a few years ago and gave up on it, but the hardware and software has gotten much much better. The difference over what the ATV puts out is downright astounding!
I've long been aware of the issue of "judder" when playing back content authored at 24 fps at 60Hz, and the ATV will ONLY output at 50Hz or 60Hz even though my TV can do 96 Hz if it detects it's getting a 24 Hz signal. I've noticed the judder in a handful of animated films I have, most notably in shots that pan across a scene, and it had really been bugging me a lot. I sold my wife on giving a Mac mini a whirl again when I showed her the difference between what the ATV was putting out vs a Blu-Ray player outputting the same movie at 24p. She can't tell the difference between standard def and high def, but this was a difference she could immediately see. Since the Mac mini is now able to output natively over HDMI since I last tried, and can be set to output @ 24Hz, it is capable of replicating what a BD player can do. Plex has gotten a lot better too and with the current Mac minis having 802.11ac wi-fi support, streaming higher bitrate video with lossless tracks shouldn't be a problem.
Going this route is a bit more cumbersome and I had to spend time in advance setting up the VNC server on the mini (so I could control it remotely off my iPad or iMac if needed); taking care to create the user accounts with very complex passwords (to avoid having someone sniffing around remotely brute force their way into it if they detect a VNC server is listening); set up Mobile Mouse (for use with iPad/iPhone); set up Remote Buddy (to launch Plex and other desired apps with my Harmony IR remote); etc. I also had to do some other basics like set the screensaver to kick on after a couple minutes of inactivity (to prevent burn-in of the menubar) and set up a photo slideshow using a bunch of photos off Interfacelift's site.
But man was it WORTH IT! The lossless audio is noticeably richer on my home theater system and the picture detail... holy moley! Even knowing intellectually what judder was and knowing it's always there, I just never knew exactly how much an impact it was having until I re-watched a few movies, and not just animated films. It's actually a bit eerie at first because we are so used to judder thanks to the mismatch between how media is filmed and the broadcast standards, but everything is so much more natural in movements and there is an increased perception of depth now.