I bottled all my competition beers this year from the keg. Out of the 10 or so that I've entered, only once did a judge note that he detected a bit of acetaldehyde which may have been the result of oxidation; however, neither of the other two judges mentioned it (including the only one of the three who was BJCP certified).
I turn the gas off to the keg, burp out most but not quite all of the pressure, purge the bottle with CO2, fill from the tap, and cap on foam.