Well I was happy with the new Marshmallow update...until my WiFi stopped working. My Galaxy Note 5 did the update and now I can no longer connect to WiFi. I make a living working in the I.T. world so I did some testing. When I boot the phone into "Safe Mode", my WiFi will work. This leads me to believe it could be related to an APP. However, I have installed NO new apps in the past month. Doing a little google research this appears to be a common issue with the MM update.
My guess is now we will all have to suffer until enough people complain and Android finally figures out why this is happening and releases a fix. Which by my estimation will not be any time soon...