I've been using these pens for two years. Before that, I hated using pens- I stuck to mechanical pencils. I hardly press down when I write, so I find it annoying to use regular ballpoint pens. I first received one of these pens from a teacher of mine, who had a family member that helped develop this pen. From then, I was hooked! I could write without having to dig into the paper, and now my writing was actually visible- a stark contrast to my previous barely-there pencil marks. The pen is comfortable to hold, and stylish. They refill with the 207 ink cartridges. I vastly prefer the 0.7 mm thickness to the 1.0mm (way too thick) or 0.5mm (so small that I had issues with ink coming out).A few things- sometimes the rubber grip stretches out at the top and begins to twist around, bulging out from the pen. I've never had the grip slip up or down- I think it's fixed at the bottom. I also find that I sometimes have issues with the blue and red ink cartridges- where it'll stop writing despite being more than half full, where it'll work if I scribble in the margin, but not when I actually try to write. I have had far fewer issues with the black ink cartridge, and thus, despite my love for the shade of blue ink, have switched to exclusively black. Even still, I sometimes experience variance in line thickness- sometimes the ink will run very thick- even too thick- and sometimes it will run a bit thin. This doesn't affect the pull of the pen, just something I noticed, Also, the ink WILL smudge for a couple of seconds after writing. Finally, this ink will not dry at all if used to write on top of White-Out.I love this pen more than I love most people, and have purchased it and its refill cartridges many times, despite it costing far more than regular pens. It's worth it to me, though I'd love to find out who keeps stealing these from me. Honestly, that's the main reason I keep having to buy them- they're so wonderful that people take them. Regardless, buy them, and guard them with your life- once you start writing with these, you can never go back!PS- they're much cheaper here than in any store. I purchased these for slightly more than $1/pen, whereas in store, I usually find them for about $2/pen.