The new Arc Soft noise reduction competition just announced seems to rely on stacking of multiple images.

This is an old technique that has presumably been refined with dedicated software.

I recall when the K10D came out, some articles about using the multiple exposure setting in the camera to reduce noise. One has to keep the camera rock steady and take as many multiple images as you can do and then let the camera do the software magic.

This is also a good techniques for intentional blurring of moving subjects, such as flowing water. It overcomes the absence of neutral density filters in bright light by reducing exposure time and combining the resultant shots.

Arc Soft has presumably built in image alignment functions to overcome slight shifting or shaking of the camera when taking a burst of images. Even on a tripod, the mirror slap will impart small vibrations into the camera.

The limitation of the Arc Soft software seems to be that their NR will only be effective on multiple shots, which implies static subjects and a stable shooting position.