The only thing I would guarantee with Delta is, they will change your flight time sometime before your trip. Which isn't always a bad thing; I always book the cheapest available flight on Delta when the fares come out, wait for them to change the times and then call them and get the best flight they have available. This year when they changed my flight back in January, I called them up got the flight I wanted and now we're flying comfort class for free.
Good Luck All,
Joe