When I first grabbed the Liquid Pencil I thought it felt light, but not light like impressive feather-weight, but more like cheap. As I peered at the construction it looked like it should really be called a graphite pen more than a liquid pencil. It comes with a fairly small eraser, but you get a couple replacements when you buy the blister-pack. When you depress the plunger it doesn't stay in place it just goes loose and reminds me a bit of the shakable mechanical pencils as you can shake it about.
I didn't want to make any snap judgments so I used it, I wrote with it, I drew lines, I wrote sentences, I repeated with a different writing utensils and went back and forth to make sure that everything I was experiencing was repeatable.
I almost always had to go back and rewrite the first line I wrote with the Liquid Pencil. It takes a certain amount of force to get the graphite flowing, but once the proper force is attained it is easy to keep the proper pressure. The Liquid Pencil only writes or doesn't write, there isn't a lot half-way for shading or light lines. Any attempts to finger shade means you will start erasing your previous lines with your finger so it isn't great for the kind of sketching I do.
On a positive note it does maintain a good strong narrow line for great lengths of time. Because the Liquid Pencil uses a ball-point you don't have to worry about keeping that column of lead at a good angle to get a good sharp line, you get as much of the ball is touching the paper. I could see the Liquid Pencil working great for people doing drafting. From my tests today I'm not ready to have it replace my BIC AI for everyday use, but it has some potential.