It was 'playable'. More of an open question as to whether it was particularly enjoyable. To be fair it had its moments.
I last played it probably thirty years ago. For a while we used it quite heavily. My gaming group at the time ran the Falklands campaign twice.
For small scale engagements it wasn't too bad but because it was stats intensive it overloaded quite easily, so less was definitely more. We did have some epic and honestly quite nail biting sub hunts using Harpoon and the fairly abstracted air rules got used independently once or twice to establish air superiority for land based games.
Harpoon is also a game that's quite resource intensive as you really, really, do need an umpire.
Not long after, the first decent computer games started to come out and the most naval focussed drited towards that. Modern naval combat is so intense in terms of force managment and C3/C4 that computer games are really the best option. I still have all the supplements and the rules but I doubt if it will ever get played again, For starters I would need to find a 1980s/90s era Casio Scientific calculator and those have become chic amongst hipsters.
There's a new computer game, Sea Power with a vast database, extremely cool graphics and a editable scenario engine that looks like it is about to sweep the gaming world and due out this month. I've been watching the beta testing games on You Tube. Not sure my laptop would have the necessary grunt so it would be an expensive outlay but it sure looks like a lot of fun and really well researched. It 's not just late Cold War either the scenarios run the gamut from the Cuban Missile Crisis to the Gulf.
Definitely the way to do Cold War naval warfare if you have the computing power or the dosh.