Bob--
Though salt is salt there are differences, mostly subtle, due to mineral content which affects flavor, and differences that are not so subtle due to color or crystal structure. Most of the differences would be entirely unnoticeable were these salts to be mixed with rub ingredients or just tossed into the cookpot. They are instead used in ways that highlight their especial characteristics. I like Hawaiian red sprinkled on something light-colored--poached white fish, say, or deviled eggs; Maldon's interesting crystalline structure looks (and tastes) great on roasted chicken right out of the kettle or on raw carrots or cuke spears; the mineral-y marine flavors and crunch of Fleur de Sel, Guerande and Camargue salts are great with seafood like grilled scallops or seared tuna but are also welcome on good bread smeared with really good butter.
Jim--
Your wife is a kindred spirit.
I tend to have a favorite-of-the-moment where I enjoy finding things that either show off the salt or things that the salt seems 'destined' to show off. I make a fair amount of appetizers and hors d'oeuvre--little bites where interesting salt can take a starring role--so I have fun with it. If I had to choose only one specialty salt though it would be Maldon. There is nothing quite like it and nothing better sprinkled on a sliced, perfectly ripe tomato.
