Thanks to Jetpens I received a bottle of Noodler's X-feather.
Until now I've been using every colour of the rainbow but black, so this was an exciting opportunity to take a look at the three other black inks I own: Aurora, Noodler's Heart of Darkness and Parker's Quink.
I tested the X-feather in a Lamy Safari with a B nib, and Rotring 600 Fine Italic. The Rotring nib is very sharp and the writing appears almost as clear as a font. It does not feather or bleed through in this pen on any of the four types of papers I used: Rhodia 80g, composition book made in Brasil, notepads from a conference and high quality card stock.
Then I did some Q-tip swab tests with the four black inks I own, and did a quick write, also on Rhodia 80g paper with a Senator B fountain pen and Aurora Noir ink.
The X-feather and HoD appear almost the same shade, with a possible slight lead by X-feather in coverage; the Aurora seems to have a slightly bluish cast on the screen although it doesn't appear that way on the page; and the Parker Quink seems greyer than the other three inks.
The drying properties of Noodler's X-feather are excellent and dries more than twice as fast as Aurora Nero.
All in all I'm very satisfied with the ink and will be using it regularly.
Thank you all (and you all know who) at Jetpens for the gift.