I am not a lawyer nor an accountant. This is not legal advice. I may be wrong.
Bureaucracy == exercise in exploration!
First, you want to read the general information for individuals, including PN 1878a – Customs and Excise Information for Travellers Arriving in Ireland from Countries Outside the European Union.
In PN 1878a there is an odd reference to digital cameras being 0% duty, and VAT 23%. Where does that come from?
Apparently TARIC is an EU-wide system for determining duty on imports. Customs Directorate of Croatia (or whatever the name in English is) apparently also maintains their own TARIC query system with matching data.
Now we need the appropriate code. What is the code for laptops?
It's 8471410000. If you enter this code and then drill down into 'for use in civil aircraft' and 'other', you'll see that in both cases the duty is 0%, in most countries. (In Croatian mirror site, pick 'Section XVI' and 'Chapter 84'. I find it curious that the Croatian system's UI seems cleaner than the official EU system. More outdated, but nonetheless cleaner.)
Since USA is not on the list, I would presume it fits under the 'Erga Omnes' list.
Alright, what about VAT? There is a list of tax rates maintained by the Irish Tax and Customs. Laptops seem to fit under Computer Hardware – Supply, which has a Standard VAT rate. As of 1 January 2014, this rate is 23%.
My conclusion is that the duty is 0%, and that only VAT of 23% is paid.
Considering top-of-the-line 15″ Macbook Pro Retina costs $2.599 = 1877.21 EUR * 1.23 = approx 2309 EUR – versus 2649.00 EUR – we get the difference of 339 EUR that are still saved by buying the laptop from the US.
For the record, no, I did not choose to buy a laptop (nor this laptop in particular) — but exploring my options is good.