ANY machine that has moving parts has a "break in" period. Not just guns. Go buy a new car and notice how you get better gas mileage, and it runs smoother when the engine breaks in after 5-15 thousand miles. Go buy a good set of stereo speakers and hear how much better they sound after about 100 hours of play-time on them to break in the speaker cones. Same thing with a quality amplifier that doesn't even have moving parts after the electronics burn-in. But I believe that people put more emphasis on a break-in period with guns because we are usually betting our lives on them.
I have always read and been told that EVERY firearm, ESPECIALLY every SEMI-AUTO firearm needs a break-in of AT LEAST 2-300 rounds for all of the parts to sufficiently mate up and seat with each other and "rub down" all of the rough edges. And more than that if the tolerances are tighter. That goes for handguns, shotguns, rifles, etc. I don't understand why so many people on this forum don't seem to accept or understand this. Kimber reccomends 500 rounds, which is a little more that most manufacturers because their tolerances ARE tighter that most others. So what! Why would anyone bet their life on any weapon that has not been tested?
Also, just because a particular guns never malfunctions from the start, or stops malfunctioning after 50 or 100 rounds doesn't mean that is is sufficiently "broken in" already. You still need to put the balance of the reccomended rounds through the gun to achieve the desired results.
Good luck, and see how much smoother that gun is after you put the 500 rounds down range.