The Single Most Important Feature Of A Fountain Pen Is...

...comfort and balance in the hand.

Don't @ me - that's my conclusion as my pen-buying fever is beginning to abate. A nib can be tuned and flow can be adjusted. I can put up with a stingy or finicky filling system. I can ignore garish colour schemes or just save them for home. But the one thing I can't do anything about is whether a pen is comfortable to hold.

It's taken me a long time to get there, but I've finally learned that, no matter how well a Pilot VP writes, I can't get on with the clip, that the L2K looks and feels magnificent, but it's section tapers too drastically, and that Edison uses some stunning materials, but their concave grip doesnt allow me to hold the pen far enough back.

This is a necessary but not sufficient condition of course. A truly great pen needs to have much more. But if it's annoying to write with, then just forget it.