After hearing about the Matias Quiet Pro Mini on the forums I went ahead and purchased one to try out the Quiet switches. It turns out that the switches are good but the feet are terrible.
I had read about the the feet being small but I did not expect it to be as serious as it is. The keyboard literally slide away form me as I type.
There seems to be two reasons for this problem. First, the rubber feet is too small too thin and too hard. It does not have good contact with the desk, and does not provide good traction at its surface.
Second, the top half of the keyboard rests on the back of the height adjustable feet. These feet, when in their retracted position are dome-shaped; on top of that, they have a glossy finish in line with the rest of the body ,which, aside from scratching on contact with the table also provide no traction whatsoever. In-fact they remind me of the skates on the bottom of a gaming mouse. The only way to make it more slippery is if you coat it in Teflon.
There are raised flat portions surrounding the feet that acts as hinges and prevent the feet from over extending in the down positions. It seemed intuitive that these flat areas should also double as the contact surface with the table when the feet are in a retracted position. This ,however, is not the case. The flat areas are 1-2 milimeters shy of making contact with the table. The dome-shaped back of the key protrude just slightly above the flats.
The situation is improved if the height adjustable feet are extended. This gives the bottom rubber feet better contact with the table. However, since rubber feet are small to begin with, the traction remains poor.
The keyboard construction, key-cap quality, switches feel and key layout are all excellent and is rightfully praised in other posts. The poor footing is really an unfortunate but serious flaw.