I upgraded last night on my 1520 from 8.1. So far so great! It performed the upgrade and kept all my apps and data intact! It was the smoothest upgrade I've had yet of a preview build by far. Previously, I always had to start from scratch.
So far it's running amazingly well for me as well. It's much, much, much more responsive than previous builds, almost on par with 8.1.. almost. It's not draining the battery like crazy like the previous builds were doing, nor have I experienced any overheating. It's been near perfect honestly. The only issues I've ran into are:
1. Screen tap responsiveness issues linger. Sometimes I have to tap two or three times before it registers. Not as bad as previous builds but still there.
2. A few "extra" apps appear to not be working at all. Namely Network +, Hey Cortana, touch. Not sure why.
3. Store keeps trying to update IE and failing? WTF? IE? Huh? .. there are a few other apps that won't update, but nothing I would ever use (carrier apps and Lumia Help).
Other than that, this build is solid!