Its afterwards when the fun begins especially if you are in IT where Revenue might not know how to tax you and you need get a written judgement (So they don't accuse you of not paying taxes).

For example I would love to start a bitcoin related business but afraid of what decision they might make (according to newspaper last week they are still deciding)

Overall starting business here is not too bad, its growing and expanding that is hard, and misconception that Ireland is low tax, it is not nor is it a cheap place to live. Everytime i hear americans complain about sales taxes I say you seen nothing yet :D