Yes, lots of folks swear by this tool. However, each layer you cut depends on the preceding layer. So if your first rectangle was not perfectly square, the others would be slightly off as well. Also, I am craft knife challenged, so I know I would have problems with this.
I'm not super particular about this kind of thing, and as I said, I just use my paper trimmer to make all my mats and layers. I'm one of those "lucky" people who have what they call a "good eye" and can line things up straight. It comes in handy when you are sewing a seam, too.