No one likes taking 4-5 passes to get through a sheet of matboard or foamcore with an X-Acto; it's tedious, but it's also the only way to get a clean cut. However, a South Korean company called Cutra manufactures and sells the Wondercutter S, a sort of powered, ultrasonic X-Acto knife that promises to make cutting tasks easy--and can even be used to cut sheets of acrylic.
The tool oscillates some 40,000 cycles per second, but the motion is so subtle that you reportedly can't see or feel the vibrations. The action of the tool means it "breezes through an amazing array of materials," according to MicroMark, who's snapped up the North American distribution rights.
The demonstration looks good, but I wish they'd show close-ups of the cut quality: