I have used one very similar to this. It's much easier to use and less straining than using free hand knives (we call them exactos where I come from but it's the same idea).

I noticed that this one, like the one I used before, has an option to set the blade at a 45 degree angle to bevel your windows. I would never have done that free hand although you may have more skill.

Looks like a good value mat cutter and I imagine your hands would thank you. Probably will pay for itself in mat board over the long run.