GNOME 3.19.4 in the core space includes the many exciting NetworkManager 1.2 features so far up to the beta, the GTK+ kinetic scrolling on Wayland support and other tool-kit improvements.
GNOME 3.19.4 application improvements include a new Windows WiX installer for Gedit, full-text search for GNOME Documents, many improvements to GNOME Maps, support for saturation adjustments with GNOME Photos, and a power button action setting was added back to GNOME Tweak Tool.
Of course, throughout the entire GNOME stack were many bug fixes, translation updates, and other minor improvements.
The GNOME 3.19.4 release announcement can be read on the GNOME mailing list. The next development milestone is the GNOME 3.20 Beta (v3.19.90) in mid-February, which is also the point of the UI freeze and API/ABI freeze. GNOME 184.108.40.206 is planned for release on 23 March.