Ireland's strength is in the intelligence of its citizens. Providing knowledge workers (and the companies that build the products they use) a legitimate international (and EU) base makes great sense. Like when the monks of old squirreled away knowledge from the viking invaders, and saved information so western civilization could rise again after the plague/Dark Ages.
This NY Times article makes Ireland seem like a haven for extra-nationals, but, in fact, the Republic has done wonders (think, Celtic Tiger) to open the EU to U.S. and other companies, from China and Japan, for example. EU unfair treatment of Asian trade was first tackled in Dublin. And the heart of innovative financing (yes, even derivatives) can be found in Dublin's financial district. Not so mention the US-Ireland bond that is so strong, Ireland's own legal system mirrors the U.S.
Complex tax systems are meant to be scrutinized by companies' accountants, and the best value for share-holders delivered at the lowest cost. Ireland recognizes this capitalist truism.