Agree wholeheartedly with the first poster. Love the game - it's exactly what I hoped it would be.
Voices, however, are a must for situational awareness. I am ashamed to say I have hit the seabed three times during some wild evasive maneuvers, where I simply don't read the warning re the sea bed. Some sub captain I am! But with a crew who never speak up under fire, who can be blamed? ;-)
In term of "new features" voices would be top of my list. But it's a great game - consider me signed up for paid DLC. We NEED a soviet campaign. And a Seawolf as somebody else hinted would be nice.
In the longer term might even be nice to command a surface ship with a helo for sub hunting.... Just a thought. Please don't move on from the US / USSR Cold War yet - there is still much more to be done in this neglected period. In sum the message is - you are making games I like. I will keep buying them as long as you keep making them.