I was very pleased to find such a small bypass guillotine as (a) I don't like the slidey blade type cutters and (b) it makes storage very easy and you don't have clear any space to use it.
I do feel, however, that it could have done with being 1/2" wider, thus allowing markings for A5. I'm also not sure why A8 markings aren't given, when A7 and A6 are. Not a big issue, I've worked it out for myself and marked it with washi tape, but official markings would have been a nice touch.
As for cutting, I find it cuts quite well, if done carefully. I slide the pages under the plastic strip next to the blade, then have to hold the strip down quite firmly to stop the pages from twisting while cutting, but if done carefully, it works very well.
Overall, for the size and price, I am very pleased with my purchase.