I have to click launch two times before it works.
The game takes ages to launch (>1 minute), much longer than with the previous launcher. It is installed on a Samsung PCIe SSD, so it shouldn't take as long.
Once the game has launched (twice, because I had to click the launch button twice in order for it to start at all), I cannot connect to any Multiplayer Server because my session is invalid. Restarting the Launcher and Game, my PC and the Network did not fix this problem.
Other people seem to have this exact issue as well, please fix it as soon as possible.