Not delta related, but sort of relevant. A girl I knew had purchased KLM's economy comfort going from PER-KUL-AMS-VIE. Her flight was delayed getting in. When she arrived in AMS, her flight to VIEW had closed so she missed her AMS-VIE leg. She was automatically rebooked by the agent on the next flight to VIE in J. No one's really sure whether her purchasing the E+ seat had anything to do with it, but I don't think it would hurt the chances.