I've always used sea salts, but never really understood why - until I read about traditional uses of sea salt in Donna Klein's cookbook, Vegan Italiano.
In it, she explains that sea salts are specifically used to enhance flavors and can give dishes a deeper flavor, especially in the absence of strong cheeses. Her pesto recipe calls for 1/2 tsp coarse sea salt, and it really makes a difference.
Sea salt actually has a different chemical composition from table salt. Table salt is pure pure sodium chloride, but sea salt is a mixture of sodium chloride, sulfate, magnesium, potassium, and calcium.
Sea salt has a different dissolution rate than table salt and has a noticeably different "mouthfeel" (a product's physical and chemical interaction in the mouth).
However, when dissolved, experts say it is difficult to distinguish between the two.
I was intrigued to learn about the differences between the two salts - for more information check out these sites:
History of Salt
What is Sea Salt?
Q & A on Sea Salt
Types of Salt
*You can purchase the sea salt collection shown above from Salt Works for a mere $140.