Does anyone have this pen? I am unable to find reviews on it, but it seems to be on sale at a certain place. It is a piston filler with an innovative design, but I don't know much about the pen or how it functions. Does anyone have one of these that they would post about? Doesn't need to be a full review or anything, just a summary or quick snippet of your opinion on the pen: smoothness, ease of use, etc. Thanks! Tadeusz