I had exactly the same experience a couple months while flying CC from LAX to IST and back. The outbound crew was awful --- one FA in particular was one of the surliest crew members I ever seen in the sky. She basically threw food/drinks at people and then disappeared. Trash was never picked up. Water wasn't distributed after the meals. The return flight was entirely different. Crew was courteous, very helpful and attentive. I fear that TK is having the same inconsistencies in service that you see on US carriers. What makes the Asian airlines 5 star is that there service is consistent....and good.