Attitude and courtesy.

[IamMatt]

If I may expand on your post, Mike,

Umpires are analogous to judges (or justices). Much of what you say about good umpires applies to good judges. The best of them know the rules/laws, apply them fairly and strongly, and win or lose, leave the participants on both sides knowing they got a fair shake. The worst of them don't know the rules/laws, apply them poorly, and can be more concerned with enhancing their own image by hiding their mistakes or interjecting their own opinions of how things should be than with simply applying the rules/laws as written.

You and some of the other guys here are working to create more of the former and less of the latter.

You would probably make a fine Supreme Court Justice.