When I was with Delta I had a few issues that irked me...

The worst for me is when we are making announcements that the flight is oversold and we are asking revenue passengers to take later flights and Non-revs keep coming up asking if they are going to get on the flight or not...

The other thing for me is if a flight is more then 15minutes late then alot of the passengers connections in ATL were shot to heck so I would have a line of passengers inquiring about their connections and nonrevs would constantly come up to inquire if I thought they would get on or not...

Another thing, not a major issue at Delta anymore, is breaking the dress code...yes there will be some gate agents that will let little things go, but some are strict on the rules - find out the dresscode for the airline you are flying on and stick to it...if ever in doubt dress business casual and you cant go wrong...working in West Palm Beach, FL I have had to make some nonrevs change clothes before allowing them to board, even after the change in dress code...