Issue still in current experimental, version 0.48.124737

Windows 8 x64, 28" 4k monitor

I won't be decreasing DPI and having to relog or reboot each time I want to play the game and Windowed mode is absolutely tiny by default(800x600). For anyone with a similar issue with the Windowed mode workaround, you can edit the window size in ~Documents/DayZ/DayZ.cfg

winW=800;
winH=600;
winDefW=800;
winDefH=600;
...
windowed=1;

Alternatively, adding "-window" to launch options in steam creates a re-sizable Window.