Getting a visa may well be easy and efficient for an Irish National, however the following is from the state department:

Citizens of the following 27 countries; Andorra, Australia, Austria, Belgium Brunei, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, Liechtenstein, Luxembourg, Monaco, the Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Sweden, Switzerland and the United Kingdom, may be eligible to travel to the United States visa free under the Visa Waiver Program if they are traveling for business, pleasure or are in transit, and they meet all of the following requirements.

http://dublin.usembassy.gov/vwp_newcountries.html