The Penxo was introduced as a very successful Kickstarter project by BitsFactory that felt the need to develop a simple and usable 2mm pencil. They asked for $8800, they received over $300,000. As I said, very successful.
Onto the pencil. It is made of a single piece of aircraft aluminum, in various colors (I received cobalt blue and black). The design is simple. The tip where the lead comes out puts pressure on the lead itself, holding it firmly in place. The center of the Penxo is hollow, so you use your fingers to spread it apart, either allowing more lead out or retracting it for pouch/pocket carry. (The hollow center also allows you to see how much lead you left.) No frills, pure simplicity.
The writing experience is nice. My fingers tends to use the hollow channel as a finger guide, since there isn't a real grip section. There is a taper down to the point, but I consistently find myself grabbing it higher. Writing with it is comfortable, (since this was written I've used the Penxo for extended sessions. No cramping or anything).
Sharpening the Penxo is a slight pain. Due to the diameter of the barrel, you have to extend the lead quite a bit to sharpen it, and the classic Staedtler 502 sharpener doesn't have a chance. I use both a KUM Automatic Long point (the blue one), as well as a sharpener from Mitsubishi. (Curious on the Mitsubishi, it provides enough resistance that sometimes the lead will turn in the Penxo without actually sharpening. Weird).
My only other complaint is the lead that it came with. The regular graphite feel quite scratchy, and for me doesn't provide a pleasant writing experience. (I'm now using Uni leads which are much better). The red lead feels terrible. It is uneven in laying down a line, so you push harder than normal. It pretty much sucks.
In the end though, the Penxo is a project I'm very happy I backed. It's a pencil I can count on using for a long time, and one I'd be willing to give to my son when he is old enough.
Original Penxo Kickstarter: https://www.kickstarter.com/projects/bitsfactory/penxo-the-most-minimalistic-2mm-lead-holder-pencil
Buy the Penxo: http://www.penxo.com/