Wow, so many good points all round here (well, apart from the now all too common threadcrap

)!
I don't know what I think now!
Focusing on the original question, I wouldn't say it adds nothing. Indeed, I would consider it
complementary to the main task, which, at the
macro level is pretty much as Neal states, at least in SH3 (ie goto AM52, sink ships, return home). Where I tend to disagree with Neal though is that at the
micro level every engagement tends to be different, requiring different tactics, different skills, different, well, everything. To this end, I can't help but think that walking through the boat will become more repetitive much quicker than sinking ships. How many different ways can I interact with "Torpedo Guy" versus an enemy Destroyer?
Of course, the "boom" crowd would disagree - they're likely to be the ones who set everything to auto and as soon as they see an enemy ship, no matter what the solution, will press the fire button...effectively turning every engagement into the same thing. So the 3D view may add more for them than for me.
Where I will find the feature not adding to gameplay is if implementing it comes at the price of more "core" features, as others have already raised here and at various times over the last five years. Then I don't care whether "Radio Guy" massages my feet and gives me a neck rub, no amount of 3D interface will make up for it...
for me.