Last year, when I upgraded from Yosemite to El Capitan, my MacBook’s wi-fi stopped working. I could occasionally connect to the internet, but only for a few minutes at a time. However, if my connection stalled out and I needed it desperately, I could turn the wi-fi off and turn it back on and get maybe 90 seconds of connectivity.
So I went back to Yosemite, only to discover that on Yosemite, on this computer anyway, Bluetooth doesn’t work at all. That’s a problem for me because (a) I often use the computer with an external monitor and a wireless keyboard, and (b) I listen to a lot of music through a Bluetooth speaker.
So I had to choose between wi-fi and Bluetooth.
As a result of all this, when the Sierra beta came out I decided to give it a try. Good news: wi-fi works! Bluetooth works!
However, now my machine won’t reliably connect to my external monitor. Ah well. Can’t win ’em all. But things have been bad enough for the past year or so that I call this an improvement.