I've been running Build 10581 in my Lumia 1020 for three days now. I performed a direct upgrade from WP8.1 without performing a hard reset, so all my apps are still installed.
1. In general so far, battery life and performance have improved from its WP8.1 state. Some apps launch faster, while the rest seem to be have the same launch time. Charging seems to be slower. Resuming and loading are still present, but are now shorter than in WP8.1.
2. Gestures BETA app isn't working.
3. New Windows Camera can take high resolution photos; tapping on the view photo icon in Lumia Camera will no longer bring the ability to reframe the image - to do this, you need to go to the new Photos app, tap on the photo taken by Lumia Camera and then tap on "Open with Lumia Camera". Windows Camera also launches faster than Lumia Camera, with similar UI and features (except Smart Sequence). There are occasional warping UI flickering issues with the Camera view finder.
4. Some tiles are blank after having the app of that tile update itself (Skype, Weather, News).
5. Background image in the App List becomes un-dimmed right after exiting an app; swiping to the start screen and back to the list re-dims the background.
6. The rest seems in place.