I set up a company recently by going through Registeracompany.ie I got the documents I needed and got my company registered with the CRO no problem. I got funny looks from my solicitor and accountant because it's not the normal practice but it can be done. My only advice: Retain copies of the articles and memorandums of assocation and get them bound along with a copy of your Certificate of Incorportation. You will need this to set up a bank account. Also, you will need to get a company seal - there are plenty of companies on the internet that sell them and they generally cost €50 or so. Also, I notice that people claim it takes several weeks for the CRO to register you unless you go through a third party company and that may be so, but it only took two or three weeks which isn't outlandish.
If you are competent with administration, then I would say there is no problem doing it yourself.