First of all great start with the Alpha guys!! I've had AAA titles that worked a lot less well on release than yours does in Alpha.
Have been playing the game for two days now and have had very few problems during play. Had only one freeze while in-game. Sounds kept going and when I fired my weapon I would hear it being fired but the screen was just frozen.
HOWEVER! The game tends to freeze on me a lot, and 98% of these freezes occur on the loading screen. I have literally been unable to complete any mission. I read about people getting after-battle reports so I know this isn't a global problem, but I would not know what this report looks like. Whether I need to end a mission because I have to turn off the game, or die three times or completed the mission, the game will ALWAYS freeze on the loading screen to take me back to the command bridge. It never gets past that. The music will always keep playing but it won't go past said screen.
Wouldn't concern me too much as it's an alpha but I'm getting reluctant to put the game back on as the only way to get out of the game is to do a hard reset... Alt+F, Ctrl+Shift+Esc don't work. Ctrl+Alt+Delete does work and I can open the Task Manager from there but the game won't allow me to go to the Task Manager to shut it down. I can Alt+Tab to the Task Manager but it will always jump right back to the frozen game.