I been going between two keyboards recently, Filco Ninja TKL with browns, and WASD with browns+o-rings. Since these are not the exact same keyboard, I'm not 100% sure how this changes the sound and feel. But when I ordered the WASD, I figured it was worth trying out the optional o-ring to see if I would like them on the Filco. I was also planning to use the WASD as a work keyboard and wanted to make it as quiet as possible.
After spending some time on both keyboards, I agree with the other posters here that the sound is more muted, the dull "clack" is lower and not as intense. But I feel like the snap from the non-o-ring keyboard. Hard to say but it feels almost too quiet. I still like both, but they do feel and sound different.