Dublin Airport has a very crowded security area. There are two at either end of the check in area (and either end of the shopping corridor airside) and are usually queued way out towards the check in desks again. Security staff can be a little rude at times. Once you're through security you're straight into the shopping area which is a very cramped long corridor with many expensive shops and lots of hand luggage rolling around. No seating until you get to the relevant Pier. I have flown mostly from Pier D in recent years and it is actually very good. It is spacious and quiet and has some cafes and shops along it. The last time I flew they still had some of the portacabin pier left (you go through a gate a Pier D which actually just brings you downstairs to the horrible bit) and its like you're standing in a caravan its very very cramped noisy and hard to hear the announcements. Very busy during the delays 2 years ago after the ATC meltdown! Landside there is a good selection of cafes and restaurants on the mezzanine above check in. Beware though all the lifts (except pier D) seem to be quite dodgy especially the ones out at the car parks even the newish lifts at check in sometimes don't work!