This is a major release with a lot of improvements (though possibly higher than usual chance of bugs). You'll need to update all nodes in your net with this version (or a later version) because at a protocol level there have been some changes. This is hopefully the last time the protocol will change before 1.0.
Major changes listed below (many smaller changes also):
- @mehuman improved the device install scripts and documentation
- @Dafeman fixed bluetooth pairing when you are unlucky and the PIN was a number less than 100000.
- Cryptography is now basically feature complete (though not reviewed by a crypto expert). Every channel is protected by an AES256 key and a rolling cypher.
- NRF52 based boards are now mostly supported (in addition to the ESP32 boards)
- TBEAMs will now charge faster than they used to
- Reliable messaging is now mostly complete (both unicast and broadcast). You'll need to update the android app though if you want to take advantage of this - see other thread.