Ok so I've had mine for a few hours and figured I would start a thread instead of cluttering the availability threads.
I'll go first:
a) Like some others on this subreddit, I am having problems with Plex, with stuttering video and other problems. This is both on wireless and via a USB ethernet adapter.
b) The TrueHD and DTS-HD lights on my preamp don't light up, so it appears that this box only supports the older DTS/Dolby codecs and not the latest lossless ones like the Shield does.
c) I ordered from Walmart online and picked up locally, the guy I picked up from told me that they're not supposed to go on sale until Monday but let me pick it up anyway.
d) Some apps are buggy. WatchESPN will conk out occasionally on launch with an error (that can be cleared by clearing the cache). Netflix is hit or miss, when I put on Law and Order SVU it played great for 3 episodes, but putting Jessica Jones on causes stutter(?) on every episode.
e) Harmony software picked it right up and was straightforward to set up. I'm not going to say easy because that word and harmony's software don't belong in the same sentence, but that's another discussion.
f) You need to wait about 10 minutes for all the included apps to get updated when you first sign in, during this time the device will be a sluggish hot mess. All those apps in their little Xiaomi section come built in, which means after all that you'll need to go back and remove the ones you don't like.
g) Like the Shield, it's pretty easy to turn off the customizations and go stock: http://android.stackexchange.com/questions/159469/how-do-i-turn-off-the-customized-xiaomi-menu-on-the-mi-box
h) I've never seen my shield do this but when you load up the home menu sometimes the tiles load in very quickly but pixelated, and then the higher resolution tiles snap into place. I don't think I've ever seen my Shield do this. It's not a big deal, I just thought it was interesting to note.
My final TLDR: It clearly needs an update, and the Walmart guy telling me that it was supposed to go on sale on Monday leads me to give it the benefit of the doubt until an update or two, the sheer amount of apps that had to be updated on first boot also leads me to believe that the software image put on this thing has to be older. I plan on holding onto mine and depending on how fast the updates come from Xiaomi might purchase another for another TV. For my main box then the Shield is clearly superior (as it should be at that price), but if they can iron out the kinks this could be a great device for secondary TVs or people not willing to shell out for a Shield.
If you want to get rid of the Recommended Apps section, do the following:
Go to Settings -> Apps
Look for an app called "XiaomiLeanbackCustomizer" in the running apps section
Force Close it
Set Notifications to "Off"
Now you get a much cleaner Recommended shows section (which is easily customizable) and the Apps section.