Yes! The exact same thing happened to me, very weird. The phone would connect to wi-fi only when it felt like it, and even when it did, the wi-fi toggle in the action center would sometimes appear to be toggled-off. If you wanted to go to settings to double-check the connectivity, the phone would be stuck on trying to load settings, which would then result in a crash/freeze. Trying to open any app was a challange, especially with Spartan, you'd have a guaranteed Loading/Freeze, which if you wanted to get out of by calling the multitasking (longpress on back), would result in unresponsive capacitive-keys so you'd have no choice but to soft reset. And after soft reset, cellular data would stop working for which you would need another reset, etc..It was quite a nightmare.. And as you said, it started happening yesterday completely out of nowhere, I was suspecting I had done some physical damage to the phone. It is very interesting to see that multiple people started seeing these exact issues on the exact same day. (I'm on a L920 btw)
I also downgraded to 8.1 and it is like heaven right nowHowever I will be upgrading to 10136 since it is said to be quite stable (even Gabe uses it as his daily driver)
same exact thing for me as well. been running 10080 since it was realeased for my lumia icon on Verizon. had the usual daily problems but never like what just happened, it was completely unusable after no significant change or update to any specific apps or settings. went back to 8.1 as well in light of 10136 and realizing how much I've missed the efficiency. was debating on 10136, I might wait for one day to see what people say.