This one is the first non-hotfix release we've done since starting the private alpha of the upcoming Vengeance of the Machine expansion.
The release has a number of non-expansion changes that we hope help (we're particularly curious to hear how that target sorting performance improvement works out), but the main addition is the new "Showdown Devices" minor faction for the expansion.
Won't spoil the details on the faction for now, but we will mention the ultimate point of the faction: provide another alternate way to win, and an ultimate stalemate-breaker :)
This is a standard update that you can download through the in-game updater itself, if you already have 4.000 or later. When you launch the game, you'll see the notice of the update having been found if you're connected to the Internet at the time. If you don't have 4.000 or later, you can download that here.