It's out, got it, and just sunk my first November. 
It really is very much like the old game Red Storm Rising. Dynamic campaign with strategic map, and tactical encounters when you make contact.
It's just the right balance of detail in sensor and weapons modeling but not getting into too deep systems "switchology" to prevent the player from having fun.
That was the problem I had with the older Sonalysts sims (688i etc.), where I enjoyed learning to use the passive sonar and plotting contacts with TMA, but never really managed to actually play the game underneath.
EDIT:
One thing that might be important for some people:
You can't directly set course, depth or speed in the game, you actually have to drive the sub using planes, rudders and ballast using a few keyboard commands. So there's no "periscope depth" shortcut or something. I find it actually works pretty well, and gives a more direct feeling of controlling the sub.
Edited by Der Zeitgeist, 05 June 2017 - 1416 PM.