I actually still have a K6-2+ based Sony Vaio at home with a whopping 256MB of RAM running Puppy Linux. When we bought it for my wife, it was state of the art and came pre-loaded with Windows ME (that was removed within minutes of opening the box and replaced with Win2K).
Even so, if I had to guess, the 3DNow! extensions were likely never used on this machine as it was never used for games.
Regardless, it is cool to discuss these changes in the tech landscape.