Recently brought my laptop from Cork to San Fran via Heathrow airport and had no trouble. Some airport security want the laptop in the bag and other want the laptop out of the bag.
Had no problem using it over their either.
No problem with customs or security, I bring my laptop with me all the time and I fly to the US at least 4-5 times a year.
You will need a plug adaptor (from Irish plug -> US plug) that you can buy at Dublin airport.
Customs may ask to have the battery in your laptop removed for inspection, and you will always have to go through security and place your laptop in a separate container, but that is all.
Your machine will work perfectly in the States.
Make sure that the laptop power supply can take c. 110-240V. In the unlikely event that it's 240V only then you will need an alternative power supply in the US.