I have been using this for several months and it has been cutting straight lines, which is what I got it for. But I do have some complaints. The markings aren't quite accurate on the one I got. There are two grids, one on each side of the cutter and one is right on and the other is off a little. This wouldn't be a problem but I can't always see the accurate one due to the paper covering it.
Another problem is that that you have to guess exactly where the blade will cut. There is just a trough where the blade cuts but it doesn't give you a precise spot so you have to learn with experience to get it about right.
Another skill you must master, since the gridlines aren't very helpful, is to try to press it against the shallow plastic guides at the top edge, which are, thankfully, precise, but they only stick up a small fraction of an inch so you have to develop the talent of pressing the paper firmly against them (with some finger pressure from above) but gently so the paper doesn't jump over the guides.
(Not important, but I think the color is ugly. Sure I could see that in the photo, but it is the only compact one I could find that would cut a full 11" sheet.)
Bottom line, if you need a compact paper cutter for full size sheets and don't mind some training time at the beginning, this will do it for you.