Normally when flying you check-in, go through security, and do immigration when arriving in the country you are going into. The US government has come up with a new system with some countries where you go through immigration at the leaving airport and Ireland is now one of those places. So instead of planning two hours at the airport when flying out you need to now plan three hours.
As is usual you check-in and go through the security check. Then you follow some signs, and find yourself at the US security check. Yes, that's right the US government doesn't trust Irish airport security to do a good enough job so they make people traveling to the US go through security again. Because it's so much fun the first time, you get to wait in a really long line to do it again. Yet, not finding this to be enough of a pain in the ass, you leave security to go into another line and wait to deal with customs. After waiting in that line, you get to the customs officer who pulls up a picture that was taken of your luggage to confirm it is yours, does the usual customs checks, takes your picture, and eventually lets you through.
So now we have to plan three hours to get out through the airport, three lines to wait in, and look forward to the day when it will take a full day to get through the airport. All in an effort to make the mindless monkeys in my country feel safe. Safe from those terrorists who always seem to be winning at making life more miserable for the rest of us. And don't use a camera to take pictures of the long lines. I saw a security guard take away a guy's camera who was snapping a picture of the lines.