There is something pleasing about writing with a fountain pen. The way the ink flows and the pen glides on paper is just a very different experience. There are also so many different things to geek out about.
- The way the nib is shaped. (Round Nibs, Italic Nibs, Flex Nibs)
- The way that it draws ink down the nib and onto the paper with capillary action.
- The way you fill the pen. (Cartridge, Converter, Piston, Pump, Vacuum, Bladder)
- The ink formation and the properties thereof. (Color, Saturation, Lubrication, Wetness, Viscosity)
- The paper qualities. (Weight, Thickness, Absorbency, Opacity, Surface Smoothness)
- The pen body ergonomics. (Weight, Balance, Grip Size, Length, Grip Shape)
And all of this is really before you get down to the actual visual aesthetics of the items themselves. There are pens out there elevated to such a high degree of art I would be afraid to use them for fear of damaging them.
As a related hobby I've gotten into Calligraphy, and have been trying to clean up my abysmal Palmer Cursive. At the moment I'm ending up with some amalgamation of Palmer Cursive, a basic Italic Cursive, and Chancery Italic.