First, there's a big difference between being sited at the coast in general and being so close to the sea that the sensors regularly get drenched in spray. Obviously, the latter is much harder on the sensors, though that said I've known at least one Vue ISS that was mounted about 2-3m above the sea surface and was still reading OK for 2-3 years at a time before the ISS (or at least the sensors) needed replacing.
But there are many Davis stations sited at the coast, eg on poles or cliffs above most of the wind-borne spray. These may need their T/H sensors replacing say every 3 years, give or take - that's a non-trivial but not huge running expense. And the anemometer bearings will not last as long, but still would typically be good for 3-5 years.
The Davis ultrasonic anemometer is claimed by its manufacturers (not Davis) to be especially resistant to salty environments but I've not seen any independent confirmation of that and is only calibrated to 40m/s wind speed (ca 90mph), which may not be high enough.
Bottom line: If the ISS can be mounted clear of the worst of the spray (even in stormy weather) and the owners factor in that the T/H sensor and wind speed bearing are considered consumables with a life of eg 3 years or so then I wouldn't have any qualms about recommending it. (And TBH I'm not sure that any other makes fare much better, especially for sensitive sensors like temp/humidity.)