Just did it tonight to my trusty old Model M...And I'm loving the results! What the foam does is basically kill the high-frequency ping/click sound you get on key rebound. If done right, you preserve clicky goodness while lowering the perceived sound level noticeably. The keys also feel a bit more "cushiony", and the resistance is a teeny bit higher. I do like how it sounds now. I'm typing right now on it and it definitely has improved the experience for me. I guess my co-workers will be a tad happier now when I go machine gun on the keys!
The trick is to use a short length of foam. After putzing around with different sizes, I used around 1/4" per spring, and made sure that the foam went down to more or less the middle of the spring. If any of you guys want to "silence" your keyboard a bit, give it a try!
On another subject, I'm a natural modder, and I like to put my personal imprint on everything. I was looking at the gray Unicomp keys available ($25 for the whole set), and thought about the gray ones. But on pics they seem a bit too bluish, which would look rather bad against the IBM soft white. Can any of you guys confirm if this is true for the Unicomp gray keys? Are they too "intense" and kinda bluish?
Thanks!