This update include an exclusive new feature to FA : Cooperative missions.
Currently, these missions are the original FA campaign, with all FAF graphics improvements, adjustment for cooperative difficulty, slightly better campaign AI and additional secondary objectives (thanks to gregory1001).
Later, original Supreme Commander campaign will be added and available if you own the game.
Domino and Ze_PilOt are also working on a campaign Editor to ease the process of making user-made campaign : https://direct.faforever.com/forums/viewtopic.php?f=45&t=4756 (some videos in the latest posts).
The lobby is now frameless (no standard windows titlebar).
Theme modders can extend their theme to tweak these new features, like altering the close/minimize/maximize buttons (with the _inactive/_active feature added some versions ago), as well as buttons/title look :
This special rule in the CSS will change the FAF titlebar text.
Will control the look of the close/minimize/maximize buttons.
The menu bar is also tweaked (check the default CSS).