If you haven't used one yet I recommend going out and buying a cheap disposable one to see how they really are.
I only own two pens but hope to acquire more. They are a MUJI and a Jinhao pewter Dragon's Descendant. The Muji is in the second and third picture and the Dragon's Descendant is the fourth and fifth.
Step 1: History
The first fountain pen was made in In 953, Ma'Äd al-Mu'izz, the caliph of Egypt, demanded a pen which would not stain his hands or clothes, and was provided with a pen which held ink in a reservoir and delivered it to the nib via gravity and capillary action.
The nib of the fountain pen was introduced by the German inventor Friedrich Soennecken. Today, the nib is usually made of stainless steel or gold, with the most popular gold content being 14 karat and 18 karat. Gold is considered the optimum metal for its flexibility and its resistance to corrosion, since fountain pen inks tend to be somewhat acidic or alkaline. Gold nibs are tipped with a hard, wear-resistant alloy that typically uses metals from the platinum group. The tipping material is often called "iridium", but there are only a few penmakers that still use this metal in their nibs. Steel nibs may also have harder tips; those with un-tipped steel points will wear more rapidly due to abrasion by the paper. The nib will adjust itself more readily to the user's style as it wears down.
Fountain Pens Today
Despite the perceived heightened prices in the modern niche, good quality steel and gold pens are available inexpensively today, particularly in Europe and China, and there are even some "disposable" fountain pens available. There are many fountain pen users around the world, even today. The main reasons people seek fountain pens in recent times are for: effortless writing and comfort (some sufferers of arthritis are unable to use ballpoint pens, but can use fountain pens), expressive penmanship and calligraphy, longevity (fountain pens are known to last several lifetimes, whereas ballpoints are disposable), professional art/design, wide range of ink colours available, recreational collecting (history and heritage), and academic benefits. Many users also mention that fountain pens retain a sense of timeless elegance, personalization and sentimentality that computers and ballpoint pens seem to lack , and often state that once they start using fountain pens, ballpoints become awkward to use due to the extra motor effort needed and lack of expressiveness.
Thanks wikipedia :P