Re: From across the pond
Edit: Sorry Brandon, I missed your mention of "moving to Ireland". The following instead refers to setting up in Ireland for tax, but still working from the US, but I'll leave the comment up. Guus has answered your question accurately.
Corporation tax *RATE* isn't necessarily the main draw for companies to solely use Ireland for tax purposes. It's a draw for companies to use Ireland as a genuine base, but those doing it exclusively for tax are using it for a different reason than the rate.
Rather, it's traditionally been due to weird incompatibility between Us and Irish/EU tax and IP licensing laws. In particular, different views on who should be taxed for income generated in different jurisdictions, which can be played off each other to say neither the US nor Ireland have any reason to deserve the tax.
These loopholes are slowly getting closed, so you may have missed the boat, but it would have been potentially a viable tactic for you, depending on the nature of your contracting work, had you considered this a few years ago. You'd want to have had substantial income though to cover the costs of the tax lawyers to set it up, as you'll need a couple of Irish companies.
As mentioned, you'll get hit for US tax when it gets repatriated, but if you only take a small fraction of your income back to the US to live off, and use the rest to buy tropical islands, then you're probably ok. Apple has billions upon billions in Ireland or Irish linked companies that it can't repatriate to its shareholders, due to the tax bill it will get. You would be in a similar boat.