Seems I'm always on a plane heading to/from IAD.
I am a regular on America West...err...US Airways. By far my worst experiences flying have been on Delta and United. The flight attendents are the worst in the air. Incredibly indifferent to your needs/concerns. My boss forced me on a United flight to Japan early this year - LAX to NRT on a really old 747 with malfunctioning single video screen and 50 year old attendents with bad hair dye yelling "beef or fish?". I got to experience the joy of Singapore Air on my next Asia trip - I can't recommend them high enough. Funny thing is my Sing air flight was nearly $700 CHEAPER than UAL.