I've got one of the Logan hand ones but it has a matching ruler with a channel that the cutter runs along as a guide. Works great... stops you wandering away from a steel rule. I think its called a 'Adapt-a-rule'

As everyone has said... change blade often. Also pay attention and learn what happens at the start and finish of cuts. Because the blade pokes in at an angle, I find I have to start the cut inside my marked line and finish after the next marked line. Hopefully you end up with no overcuts and the cut bit drops out without any extra work with a blade!!!! I cut on an old piece of matt board (on top of a self healing mat) as I find the self healing mat is too tuff for the blade to run along/in smoothly. With the matt board base you can run the blade a bit deeper to ensure the cut is clean. Nothing worse than not going right threw the one your cutting (well there is one thing.. cutting from the wrong side of the line). The other trick I learnt from someone, was to rub the edges of the cut window with the back of a spoon. Just softens them slightly and IMO looks better. Try it on a test cut and see what you think.