I had one. Liked it. But my preferred tool for upholstery was a PMF dry technology tool.
The tool worked as advertised, as far as I know. The drawbacks were- it used too much water for convenience with a portable, and I did lots of furniture with a portable, especially in high rise condos.
The PMF would go through an average of 10 gallons for an average sofa, the
Drimaster would need about 15 gallons for the same sofa.
I did mainly use mine connected to the Truck Mount. I used it on cotton chenille, and chintz, regular nylons, and tapestries, and heavily soiled items, because the heavily soiled items needed more water and solution than the PMF would put out.
Most of my jobs were cleaning lightly soiled, and delicate fabrics, and that's where the PMF tool shines.
So, it depended on the fabric and the soil load which tool I would use.
I like having more than one tool in my toolbox.
Gary