My own experience is that Guinness does, in fact, taste better in Ireland than it does in the U.S. It's pretty easy to ascribe that to freshness, though. Any beer will taste better closer to its source.
Over a period of one year, four researchers of different nationalities traveled to 14 countries and visited 71 Guinness serving establishments in 33 cities to collect data for 103 tastings.
Tasting scores for pints of Guinness were generally high all around the world, yet tastings in pubs in Ireland scored significantly higher.
Read the whole story at Science Daily.