If the day is shorter by 3 microseconds, that would translate into a milisecond per year. That may not sound like much, but for some applications it could become significant. For example, unless GPS satelites are recalibrated (which I would expect should happen), the change in rotation would cause logitude readings to vary by half a meter per year at the equator.
Yep, for navigational purposes, especially in the open waters, 3 microseconds is a big deal.