Depends what you want out of it.....
Worth it if all you need is .....
Cheap Android TV experience with 2.0 audio 1080p / 4K HDR Netflix / YouTube / Kodi etc. video streamer.
And for that you need decent home dual band AC WiFi if you want half decent functionality - out of the box.
Even then do not expect 100% reliability.
Start getting too demanding and needing features like:
- auto Frame Rate Matching for silky smooth video playback when using Plex, SPMC or Kodi..
- Kodi HD audio passthrough
- working 5.1 Netflix audio
- high quality deinterlacing from an external TV Tuner server...
- proper Dolby Digital audio support
- reliable sleep / wake up functionality
- ultra reliable Chromecasting
And the wheels will quickly fall off.
The faster, more powerful 2018 Fire TV Stick 4K has better Firmware support from Amazon and is feature packed if you can put up with Amazon's pushy user interface.
The NVIDIA Shield is another league all together vs the cheap Android TV OS devices.
It's not top of the line, but for $40 it's pretty good. It's capable of 4K chromecast, which if you buy from google is $60 - and that device isn't even an android TV, just a chromecast. And if you're one of the lucky ones (like me) then you will have few issues. Mine has been great, plays 4k streaming just fine, no locking up, remote works, etc. However, a lot of people seem to either get bad units or something about their setup makes it not work well for them.
No. Fire Stick is better and Nvidia Shield is best
I bought one for $40. If the androidTV experience is really important to you and you don't have the cash for a shield, I suppose then the mi box is your answer.
The wifi just randomly stops and starts. The remote randomly will unpair and then repair. The box has locked up a couple times and required power cycling. All this and I've only had the thing for a couple weeks. Buy a shield if you can afford it, if not, FireTV stick for 35 bucks in my opinion.