Not necessarily a faster feedback, but they reduce the distance your key travels when you press it down fully. It still registers the key press at the same distance, but if you always seem to bottom-out, it will be a bit easier to move from one key to the next. If I had to describe the comparison to stock keys, the o-ring mod makes it feel more fluid IMO.

O-rings are placed around the switches on a mechanical keyboard. Using them is a personal preference, so they may be terrible for someone but great for someone else. I very much like how they feel.