My take on the Xiaomi Mi Box...
Bought this on Friday from Walmart and set it up today on my receiver with a 1080p projector and 7.1 sound system. I love streaming boxes and have quite a few currently, AFTV, AFTV2, AFTV stick, ChromeCast 2, Roku 3/4, and the Nexus player.
This is much snappier and more responsive the then Nexus Player plus my Nexus player has issues with videos skipping in Netflix and You Tube, I saw none of this from the Mi Box. I like the Android TV UI, it's better then AFTV and Roku but there are a couple things about this that are a deal breaker and I'll probably be returning this.
Review of some of the apps that I tested with:
Netflix - it's perfect, fast and outputs DD+ 5.1
Hulu - doesn't support 5.1 sound on any platform, but works as expected
Epix - doesn't support 5.1 sound on any platform, but works as expected
Google Play movies - outputs DD+ 5.1, ramps up to HD quickly
NBC News - works as expected
PBS Video - works as expected
Showtime Anytime - doesn't support 5.1 sound on any platform, but works as expected
Pluto TV - works as expected
Vudu - UI is ok, not that great really, very slow ramp up to HD/HDX, doesn't output DD+ 5.1/7.1 for some reason
CinemaNow - UI is ok, Does not support DD+ 5.1
FX Now - works as expected
Haystack TV - works as expected
HBO Go - works as expected doesn't support DD+ 5.1 for some reason
You Tube - Works as expected, supports 720p/1080p60fps which is nice.
Ted TV - Works as expected
Comparing this to Chromecast2 @ $35, Chromecast is the better deal IMO because Netflix, Google Play movies, Vudu, HBO Go and CinemaNow support DD+ 5.1, there isn't a Android TV app for FandangoNOW but it can be cast and it supports DD+ 5.1 on Chromecast2 but casting to the Mi Box it's only PCM 2.0.
Android TV is lacking in apps also, surprisingly there are a lot of apps MIA for Android TV, but you can cast many that don't have a native app which does make up for some of them that are missing.
If your looking for surround sound within most major apps on the Android TV Mi Box then you will be disappointed as was I, but if you have a 1080p or UHD TV/HDR with a 2.0 soundbar then it's a great little box for $69.00. If your looking for UHD/HDR with surround sound then the Chromecast Ultra for $69.00 looks like a great deal.
Unfortunately for me the Mi Box is probably not a keeper because many of the major apps are lacking surround sound.