I used to fly to the US regularly, usually on the 10:10 Ryanair Cork-DUB. Arrive at 11:00 to catch the 12:50 to Chicago. On the return, I arrive back in Dublin at 8:25 and onwards with the Aer Arann 10:15 flight to Cork.
I should have been clearer in my previous post that I use both Ryanair and Aer Arann on the Cork-Dublin flights as there are 6 flights a day!
I only fly via LHR or AMS to the US if the destination is not available from Dublin.
Have to many bad stories connecting through LHR losing bags, long lines at security, changing terminals etc.
Dublin's great advantage is that the flights are cheap, it is easy to connect as there is only one terminal but its greatest advantage is being able to go through US immigration in DUB so I get to skip the long INS lines at Chicago O'Hare!