The Irish startup visa program has recently been amended to make it easier to qualify:
http://founderware.co/ireland/ireland-launches-startup-visa-...
You now only need to invest €70k ($91k USD) to be granted residency. This is down from the old requirement of €300k.
Taxes here are quite reasonable. Corporations are charged 3.1x less tax here:
http://www.americanthinker.com/2009/03/us_companies_pay_the_...
On average, UK taxes are generally higher:
http://www.nationmaster.com/compare/Ireland/United-Kingdom/T...
And it compares favorably with the US as well:
http://www.nationmaster.com/compare/Ireland/United-States/Ta...