The preclearance will make flying from Dublin to the US more attractive to people from Northern Ireland as coupled with the recent road improvements, it will be quicker to drive to Dublin and preclear than fly to England to connect then stand in line for up to 2 hours as I have done at the US point of entry. It will also erode the value of the Continental BFS-EWR service (maybe that is one of the reasons it is rumoured to be going down from daily this summer to 4 per week in the winter (5 per week last winter)