Seeing as how salt is used in almost everything we cook, I thought I'd offer up my thoughts on it here.
A few years ago when I first started noticing sea salt coming into the mainstream, I totally scoffed. I chalked it up to just a marketing gimmick-
"Our potato chips are better because they're made with Sea Salt."
Yeah, right. "Sea salt & vinegar" potato chips are only different from "regular" salt & vinegar chips in that they cost more. Or at least, that's what I thought. Then I started reading some BBQ books by Steven Raichlen. He recommended using Kosher Salt as opposed to table salt. Said it didn't burn your tongue the way table salt would (in addition to being easier to sift through your fingers due to the larger size crystals). That got me re-thinking about sea salt, so I went home and did a simple taste test with sea and table salt-
First, I just tasted a pinch of sea salt- didn't notice anything unusual; tasted like salt. Then I tasted a pinch of regular table salt. What a difference! The table salt had a harsh, burning taste to it, not "clean" at all like the sea salt. Later on, I went out and tried some sea salt & vinegar potato chips. (I like salt & vinegar chips anyway, so it was some tasty research.) Big difference there, too. Although tasty, if you eat regular salt & vinegar chips, you'll notice that after awhile your mouth will burn and sting from the salt; not so with the sea salt variety. Marketing gimmick or not, it really is better. (Not to mention that if you throw it in a pot of cooking water, like for pasta or something, it will foam up a little, like ocean foam : )
All salt is not "just salt". I'll never use table salt again. Maybe the harsh taste of it just comes from the added iodide and un-iodized salt won't have that harshness. I don't know; I haven't tasted the un-iodized kind. Maybe that makes me a food snob. Maybe I don't care. I'll continue to use both Kosher and Sea salts. Sea is a little more expensive, but you can get it fairly cheap nowadays, and find it almost anywhere. Hain and Morton both market a commercial variety that you can find in almost any grocery store, and if you have a co-op or natural foods store nearby, you can usually find it in bulk for less. When I need a large amount of salt for a recipe (like the sour pickles I'll be writing about before too long) I tend to use Kosher. For smaller amounts, or for sprinkling on food, I go with Sea.
You can read a little more about the differences between the three at Food Network.