This release has lots of updates and fixes to the GATT D-Bus API. It should be working considerably better now. A key change to the GATT D-Bus API is that it is now fully conforming to the word of the D-Bus Object Manager specification. Instead of registering each service individually with an Object Manager interface per service path, all application services are now grouped together through a single RegisterApplication call. The details can be found in doc/gatt-api.txt. Besides the D-Bus API change there are also numerous fixes to GATT functionality in general.
Other areas that received fixes in this release are OBEX, AVRCP and 128-bit UUID handling. Feature-wise there isn’t anything groundbreaking, but a notable update is support for the Start Limited Discovery command in the btmgmt tool (this feature debuted with the 4.5 kernel release).