The APD tax is certainly a disadvantage, being the only region of the UK with a land border with another European legal jurisdiction.
Bit off the subject but similar vein, one interesting thing I found out recently and may be of concern for those who frequently fly from DUB. Travel insurance purchased from UK suppliers do not on the whole cover missed departure except from a UK departure point. So if your car breaks down, or something happens on the way to BHD/BFS/LDY and you miss your flight, you will be covered. But if the same thing happens on the way to Dublin, generally you wont be. Aviva in Northern Ireland tried to get this changed for their Northern Irish policy holders, but was not granted. Would seem most UK insurers are the same!!!