I was playing through the Prologue, which is pretty awesome, but I found a sound bug while doing it. If a character is reading a line and you hit escape to pause, then when you return to the mission the character doesn't resume reading the line. There's just dead air until the sound's play time elapses. All the other sounds are fine. I've done it a couple of times in a couple of missions and it's fully reproducible. I haven't tested it with the standard FSO executable, but I thought I'd let you know.
Other than that, this is pretty awesome!