I have these, for an office. Yes they are silent if you slowly push and release a key, but thumping away at 50-60 wpm still makes a huge amount of noise, even with o-rings installed (although a lot quieter than blue switches which I used to have).
I have topre switches, so a bit different experience, but a friend of mine had "shown off" that indeed, you can type silently on them. It's the art of not bottoming out which is something like 90% of the noise.
