From what I understand, they have exceptionally small tolerances. So if a Glock or a Springfield might have a part that can pass inspection with a half millimeter variance, the Kimber requires the same part to carry a fraction of that.
This translates to more reliability and durability. These are meant to be weapons that last a lifetime and are passed down. There is also a lot of prestige to the name. They are truly hand-crafted and highly customized.
Now as to whether all this makes much of a difference in the field, I can't say.
Our prime purpose in this life is to help others. And if you can't help them, at least don't hurt them.--The Dalai Lama