I have tried to upgrade several times to 8.1 on the preview dev app . Everytime it was an abject failure. My phone heated up and it was always glichy. I just went back to 8.0 and stayed were I was supposed to. After cyan update, which was no noticeable difference, 8.1 showed up. From my experience I knew that my phone and 8.1 was really buggy. I went ahead and upgraded knowing I could downgrade to 8.0 and 3 weeks later my phone would be back to running good. Fricking windows phones. Are awesome! 8.1 is smooth and like a brand new phone. I love this update like a sweet piece of azz. It is nice. After the bs with the dev preview I just wanted to share my appreciate. I've got a 1520.3, its awesome and just got better.