Windows 10 Mobile build 10536 is finally here with a number of improvements, but there are still quite a few known issues with the build that you should be aware of. Here's the full breakdown from Windows Insider chief Gabriel Aul:
After rebooting your phone, you won't see notifications, such as new messages, until you unlock your phone. After that, you should see notifications for new messages just fine. "zStorage" appears in the Settings app under System and clicking on it causes the Settings app to crash.
Camera upload to OneDrive may not be enabled based on prior settings. To fix this, make sure you are running the latest version of OneDrive by opening the top left navigation bar, then settings on the right to verify that camera upload is turned on and you have the latest app (version 17.2).
Insiders will not be able to move from Slow to Fast rings temporarily; we are working on a fix but in the interim to move a device from Slow to Fast you will need to use the Windows Phone Recovery Tool to first start on Windows Phone 8.1 and opt directly into the Fast ring.
Additional languages for speech and keyboards won't be available until tomorrow (9/15) and will error if you try to download. If you already have languages for speech and keyboards downloaded to your phone prior to upgrading, they will remain and available to use.
Aul also addressed Lumia 1020 users who are disappointed that they can't take full advantage of their camera's features due to the lack of the Lumia Camera app on the Windows 10 Store. Aul says that the app will be available to download from the store later this fall, and users can either wait to download it then, or roll back to Windows Phone 8.1 to get the app back.