I was one of the few able to purchase a MiBox on Saturday Morning before Walmart shut it down. I keep seeing a lot of questions floating around and figured I would start a thread to see what I can answer for you.
Currently, I am able to confirm the the Android PS Vue app does work with a mouse and using ChainFires SideLoad Launcher to open it. It runs and streams, but the quality seems really low. 720 or maybe even 480.
My son has been playing RipTide and another driving game, and they both run very well. Casting to the device is quick and easy just like a Chromecast - it can get annoying if someone decides to cast something to it while you are watching a show or playing a game. I see fights getting started over this.
I only have a 1080p TV, but I streamed Pluto TV's 4K World channel and it's remarkably more clear and crisp than 1080 content (Maybe placebo)
I won't be able to do anything until I get home from work in another 4 hours or so, but post a question or test and I'll see if I can provide an answer when I get home.
Edit: A note on the CBS Sports app, the Android TV App doesn't show live game content (on Saturday UT vs FL) just highlights and pregame clips. So I had to cast the game from my phone to the MiBox. Wtf is that about? If that's a content distribution thing, it's stupid, it ended up on the Mi Box regardless.
Edit 2: I also plan on purchasing this to see if I can get Ethernet over USB to work if anyone has any reviews on that product or wants to say "Hell no it wont work" before I spend $30 https://www.amazon.com/gp/product/B014ZOJX7W/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A294P4X9EWVXLJ
Nah, not placebo, it should be more clear. That channel streams at a very high bit rate, higher than most streams, so even at 1080p, you will notice a difference.