I just got a bunch of these, and I have to say, I'm impressed. They feel very similar to complicated orange Alps switches (but without the plastic hitting plastic sounds), and quite a bit better (more sharply tactile) than the dampened complicated cream Alps switches from an Apple Extended Keyboard II. We’ll see if any of their feeling wears off with use / age, but at least when they’re new, these switches are great!
The one possible downside I can imagine vs. the orange alps switches is that the orange switches have a little metal leaf holding each side of the switch, whereas the Matias quiet switches just have one on one side, and the metal on the contact side is a smaller piece and doesn't exert as much pressure on the switch [typical of complicated vs. simple Alps switches]. This might make a bit of difference in forward/back stability as the switch goes up and down. It doesn’t seem like too much of an issue here though; the difference doesn’t stand out. I’m guessing that molding to tight tolerances might help a bit with that [but I’m not at all an expert here].
I’m making some custom alps keyboard projects, and if I make a version to carry around out in public, I’ll definitely opt for these switches.
* * *
It’s slightly off the subject of these switches in particular, but I wonder, has anyone tried putting some kind of padding on the top of the switch housing [not the slider, but the other part], as a way to even further dampen any plastic-on-plastic sound that might arise from the keycap bottom hitting the switch housing top (e.g. by using those stickers that some folks stick in the middle of cherry switch housings)? O-rings don’t really work with Alps switches/caps, but I think some kind of damper here might make a difference. I’ll try to do some testing sometime soon.