If I do use expletives, people complain and say (incorrectly) that 'soldiers/sailors/marines don't talk that way.' And, correctly, that it offends many people and often is not suitable for children.
If I don't use expletives, people complain (correctly) that 'soldiers/sailors/marines don't talk that way.' Soldiers, marines and sailors do use 'salty' language. But that offends many people and often is not suitable for children.
If I use alien terms, the first group is calmer because it is not things like 'sh*t, f**k and motherf**ker.' (Maulk, grapp and behanchod, respectively, although Behanchod is Rahni (Indian goatherd dialect) not Adar and actually means 'one who bears children upon his sister.') I fully anticipate some day getting an email from an offended Brahmin. (I have gotten a couple from Indian readers saying 'You know behanchod is a real word, right?' 'To which I respond: 'Not to Americans. Although I hope it catches on. It's got alot more flair than MoFo. There's nobody that can curse like a goatherd. Nobody.')
The second group understands the reasoning (generally from having grown up with golden age SF which did the same damned thing and often commented on it with asides like 'Jason could not believe that the Preacher even knew the explicit Arcturian curse word he'd just uttered which involved a form of deviancy impossible for humans to imagine given their simple two gender mating system...'). They occasionally pick up some of the words for use at, say, work.
'Grapping server, boot you piece of maulk!'
They are, admittedly, mostly geeks. Although often well armed ones.
It does, alas, create a third group which complains that 'it interrupts the reading flow.'
To which I reply, in the immortal words of Abraham Lincoln:
You can please some of the people all of the time, and all of the people some of the time, but you cannot please all of the people, all of the time.
For further background, one of the people who dislikes it is Toni Weisskopf, the publisher of Baen. But she accepts it for the historical versimillitude. The Vorpal Blade series is designed to be very much like classic SF. The only thing I've avoided is things like the Adar being big smokers and the term 'news hen.'