The Pilot Decimo is a very thin version of the Pilot Vanishing Point/Capless model available. In comparison, I think it feels slightly less robust - dare I say feminine? The VP is thicker diameter and heavier, giving it a beefier feel.
With the Decimo, I am using it with an EF nib and journaling into a Midori Passport size journal. I'm carrying it all the time. For that purpose, it's great. For longer writing sessions and when using cheaper paper, I tend to use my Vanishing Point.
My only disappointment was that it came used. It still had blue ink in the nib and the cartridge was empty. I almost sent it back for that reason. But, since I was going to use the new EF nib I bought, combined with bottled ink, I decided to keep it.
Pilot Fountain Pen Capless Decimo, Dark Blue Myca Body, F-Nib. The clear demonstrator allows you to see not only the amount of remaining ink, but the color of the ink as well. FCT-15SR-DL-F