I use one. I stencil for airbrush mostly. I replace the cutting tip with a small brass round head bolt and use it to hold a sewing needle. I run it through a soldering iron temperature control at about half power that it doesn't overheat the needle and cause it to quickly lose temper. Even so, I replace the sewing needles after a few minutes of cutting because a sharp point makes for the most precise cut.
Buy extra tips (or use Don's trick). I don't have a resistor, so my iron is always on full heat. Anyway...I use a hone (those diamond plated hones you can get from Harbor Freight) and resharpen the tips as they dull. http://www.harborfreight.com/3-piece-2- ... 36799.html
I've only used this tool for cutting thin resist. An exacto is better for thicker resist or buttercut.