Great for agitating pre-spray on upholstery prior to HWE, but you've just retired from that market David.
Texatherm do a range of brushes suitable for use on different fabrics, you could possibly spray with a shampoo solution, agitate with Minitex, then vacuum off with a wet vac. Just a thought. And Neil's right, using a pad on upholstery throws moisture all over the place.
When scrubbing stairs, especially if you're doing a lot, don't put too much pressure on the brush, there is a thermal overload on the motor which will kick in and leave you without power to the minitex for quite a while.