I'm in the use the filter sometimes camp. When I know I am going to be in an harsh enviorment like being at sea(US Navy) I use a high quality Nikon NC filter. When I go to summer camp with my boyscouts I also use a filter becasue of the large amount of dust that I would rather clean off a $100 filter than my $900 dollar lens. I have never really noticed a drop in IQ when using my Nikon NC filters but then again I don't pixel peep either for me if the picture looks good at 8x10, 11x14 maybe even 16x20 I'm good.
I feel there is a time and place for filters and there is no wrong or right answer we all have different needs. I can tell you this salt water is not fun and is abrasive but our Big Eyes on the ship have huge front elements and they are always exposed to salt water with little ill effect you just have to use a lens cleaning solution to clean them as not to scratch the lens with the abrasive salt that has dried on the lens.