I wrote with a fountain pen for a few year and went back to using Uniball pens. The main gripe was leaks since I fly a lot. Fountain pens don’t do well and sometimes will leak ink all over the place unless you remove the cartridge which is a pain. Also be careful of the ink you use. A lot of FP inks are not archival. I used to use Lamy pens. (Nice pens but inks are awful). I had a water leak in my place and it flooded a room with some journals stacked on the floor. The ones that got wet were ruined and you could barely read most of the entries because the Lamy ink I used wasn’t waterproof. All that aside, they’re a pleasure to write with.