Might I offer a contrarian point of view here?
Of course, your tracker interest rate is absurdly good at the moment (like 2.5%, right?). But, what goes down can come up, too. The article @rath3r links to claims a 100K savings, but the writer assumes that tracker interest rate will be 2.5% for the remainder of that 30 year loan.
Do you know for a fact the ECB rate will stay at 1% for the next 25-30 years? If you think so, then ask yourself: 5 years ago did you know that it would go down this far? Your bank certainly didn't.
I'd say run the numbers, and see what you can lock in on a fixed rate (it is a bad idea to switch to a variable, of course). If you can get an interest rate that's historically low, like the 4.19% mentioned in the article, I'd consider it. Especially if they also offer you other incentives, like cash incentives, and you used that to lower the mortgage amount or pay off other debt.
You could even see if you can squeeze your bank a bit, and negotiate something absurdly low like 3%, or maybe better incentives. At the moment, you're in a position of power where negotiations are concerned!
So yes, you would be paying more per month now, but getting a fixed rate would also protect you in the future. Compare what you can can get as new fixed rate now to what you were paying initially. The interest rate could go back to where you started. Also compare to what you could be paying if ECB rate went a good deal higher, like 6%, 7% or more. Remember, the current troubles are the first troubles the Euro's faced, so who knows what will happen? In the USA, in 1980 and twice in 1981, benchmark interest rates spiked to 20%. It was 10% or higher from January 1979 straight to July 1982. Could you survive even a few months of that?
For the record, I'm not from Ireland, and I had no idea tracker mortgages even existed until I saw your question.