If you have the patience to handle Iron Gall Ink, they are a pleasure like none other. It was the penman's popular choice for good reason. They produce very fine hairlines and enable swift stroke production.
Cons wise, they require a good quality paper to reflect those hairlines. Also, given its nib-eating nature, instead of a fountain pen, I'd suggest pairing it with a holder and a good nib. More hassle, but more pleasure. McCafferey's Ink is a great recommendation if anyone would like to try.
"* McCaffery's inks are highly acidic and can eat away at nibs. When using this ink, clean your nib thoroughly and often to avoid corrosion. You may also find mold on the surface of the ink, or a dried skin. These developments are natural and do not mean your ink has gone bad. Simply remove the mold or skin, throw it away, and stir the ink well. You are now ready to keep writing!*"
Uh, yeah.
Glass dip pens are generally available, though I haven't used one. I also have a glass-nibbed fountain pen, but it's mostly for pondering the weirdness of the universe.:-)
Cons wise, they require a good quality paper to reflect those hairlines. Also, given its nib-eating nature, instead of a fountain pen, I'd suggest pairing it with a holder and a good nib. More hassle, but more pleasure. McCafferey's Ink is a great recommendation if anyone would like to try.