Well i didn't play the Alpha much yet. Basically just started and have in mind to do some testing this weekend. But i already found something:
If you have 3 displays and start the alpha over the desktop icon it starts (at least that happens to me) on the most left display instead of the middle one. "Same" thing happens when you start the Alpha over Steam itself. It then starts up in the middle display but you can't navigate the main menu with the mouse & if you change back to desktop with Shift + Tab and then again back to the game it is again on the most left display :(.... but you then can use the mouse to navigate in main menu again.
Would be great if this could get a fix as soon as possible.