A small letter--a big difference

It is, I am told, the difference (addition) of a single Greek letter found in the newer manuscripts used by the Authorized Version (KJV) that causes the familiar passage to be rendered as:

Glory to God in the highest, and on earth peace, good will toward men. (Luke 2:14 KJV)

The modern scholarly translations, which use older Greek manuscripts, render it as:

"Glory to God in the highest, and on earth peace among those with whom he is pleased!" (Luke 2:14 ESV)

Juuuuussst a little different in meaning.