"How broken is broken? seriously":
For me, not broken, otherwise it would be unplayable, which it isn't in technical terms.
I won't repeat other's issues with the game, as i concur with most of them, ie. AI, Mission objectives, save games going up in smoke, some coding issues eg. lag in certain parts and scripting issues eg. campaign "flow"...
I am reliant on the mods which makes this more than playable.
I am happy i purchased the game, always optimistic about further support for the game and enjoying ploughing the Seas in 1939