I have one. They are cool because they can write on almost any surface at any angle. The writing isn't remarkable, though, and the pressurized refills are too much for how fast I would go through them.
Just get a $30 lamy fountain pen with a refillable cartridge, and a large bottle of ink. You're done worrying about pens and cartridges for the next 15 years or so.
Pretty sure they're gel. They sure as hell don't smear. And that model is retractable.
I fucking love the Space Pen cartridges. Finding the right pen body can be kind of annoying though.