I made one, but won't likely ever make another.
As Shawn said, it is a short fat pen, not entirely uncomfortable to write with, but VERY impractical to carry around. The lack of a clip would generally make it a pain to carry, being short and fat adds to that, and the fact that any quick movement in the right direction will cause the refill to extend makes putting it in your pocket a risky endeavor. On top of that, it doesn't take either Cross or Parker Refills. I haven't looked into the actual refill to see if it is any sort of a standard, but for ballpoints, we have those 2 that cover nearly every other ballpoint (my only other experience is the mini-cross used in the teacher's pen and a few other of the very short ballpoints, but it still uses the cross transmission...)
Then there is the $20 price tag. There are a lot of pens that look nicer, have better platings (the colors do nothing for me...), carry easier, and use better, more readily available refills at that price. IMO it's a novelty for us pen geeks to have just to show it can be done.