All I know is that I only have to break out my OP machine every once in a while, but damn does that thing do an awesome job of pre scrubbing.
Just did one today. Tried to just wand some pretty nasty office carpet, didn't look so great. Broke out the OP and scrubbed it up. There was still a little brownish tint to the blue carpet. Hit it with the wand and the thing looked almost perfect.
The rest actually came out better than this area but I didn't feel much like taking pictures after I put the back door of my van through the front of my trailer.
Here's some pics of it: