I came really close to returning this cutter because it shredded the corners when I first used it. The trick is to make sure the blade aligns perfectly against the bottom plate, so that there is no space in between the two pieces. I also had to adjust the guides in order to get just the right smoothness to the corner. The cutter may not be perfectly calibrated right out of the box, and the instructions aren't overly clear about this. I can see how some users got frustrated and sent it back but it does work well once you get everything aligned exactly right. The only problem I'm having is that the corners on the bottom sheet are rough and need to be trimmed with scissors. I'm currently using it to trim laminated postcards in stacks of 8, but I'm sure it will go through several more at a time.The machine comes with a few spare parts but no explanation as to what they're for. Some are obvious, like the allen wrenches, blade and oil, but the others are a mystery to me. I'm also concerned about blade replacement, the instructions don't say where to get replacement parts.