Now seemingly on an approximate fortnightly update schedule (here's the previous), the Windows 10 Mobile 'Fast ring' Insiders have a new build to play with, 14936. And this time it actually works on the Lumia 650 (yay!)....

From the official announcement:

Today we are excited to be releasing Windows 10 Insider Preview Build 14936 for PC to Windows Insiders in the Fast ring.

• We fixed the issue causing the pin pad to not be visible to unlock the phone even after rebooting the phone.
• We fixed the issue where some phones lose the ability to use their SIM cards.
• We fixed the mobile hotspot issue where it works the first time but subsequent attempts to use the feature won’t work until the phone is rebooted.
• We fixed an issue causing some devices such as the Lumia 650 from failing to install a new build with Error 0x80188308.
• We fixed the issue causing some build updates to fail with an 800703ed error code.
• We fixed the issue where Action Center no longer closes if you swipe up on the empty space (area of Action Center that doesn’t show any notifications).
• We fixed an issue where notifications were unexpectedly showing the app logo within the notification when viewed in Action Center.
• We fixed an issue for devices that shipped with Windows Phone 8.1, such as the Lumia 930 and 1520, where if you plugged in a headset during an ongoing call, the audio would not be routed to the headset.

Known issues for Mobile

• If you have your default storage set to a SD card for apps, installation of apps like WhatsApp, Facebook Messenger and WeChat will fail with an error. As a workaround, set your default location to your device’s onboard storage.

All my Fast ring devices are downloading and updating as I write this. 

Of course, in the fulness of time we'll need a summary of what's new going from Redstone to Redstone 2, but we won't have a full feature set or changelog until at least Christmas 2016. Settle down for the long haul, everyone....!