It should also be remembered that there has been a great increase in the frequency of the train service. There is an hourly departure now, which neither carrier can match.
Personally, I still tend to use the train to travel between Cork and Dublin. Although, it should be faster, it is still competitive time-wise with the plane once check-ins and trips to and from the airport are taken into account. Also, the train ticket provides greater flexibility. If a meeting overruns or I decide to stay in Dublin late for social reasons, my ticket is valid on the next train.
The only times I ever fly between Dublin and Cork are if I'm catching a connecting flight or if my final destination is somewhere around Swords or Malahide.