e/ 19.05.2019: Must revise my review below: I wrote this while running the box on a FullHD TV. Everything very smooth, no jerks. Then I bought a new 4K TV in the digitec action and wanted to continue to run the box there: In 4K video playback, I unfortunately had to determine micro stutters (both Sky, Netflix and Youtube). Remedy has only managed to switch the resolution to 4K 50Hz instead of 60Hz. Google search also confirms that the hardware is simply too weak for 4K playback. Too bad! But not surprising for the price. Further, the picture quality should not be as good as other boxes manage - or in my case, the app in the Samsung TV directly. Personally, such cutbacks do not bother me much, must look for the differences idR extremely. But still a pity...
Box went back and I now have the Nvidia SHIELD. Runs viiiiel faster and more responsive, Ruckler gibts nowhere, and in addition I can still use the many other features of the box. Great device, but not quite cheap.
The MI Box S works flawlessly, everything on the first try. I had ordered a USB Ethernet adapter because I was afraid of the WLAN problems - but then I set up the box and saw that an update is ready. There was explicitly mentioned that problems with the network will be fixed - so I had good hope and operated it once test with WLAN furthermore.
Never had any problems! No jerks, no hang-ups, nothing.... once the Sky app (for GoT, otherwise I don't know them much) crashed, but I think only because an update was installed in the background. After that, never anything.
So I can say with good cheer: the WLAN problems are fixed, don't worry about that anymore.
Android TV I find good, but the problem with the WLAN is annoying.
So that video streaming, for example, with Netflix or Teleboy work smoothly, the box needs about every day a reboot. Without a restart, it takes a long time until the videos start and then they jerk without end. If you believe the reports that can be found via Google, then it somehow has to do with the WLAN driver that hangs up. After a reboot it works fine again though.