Here is a good list of indoor aerials with recommendations:
Note the North Side of Dublin has a fairly strong signal. If you can see the Dublin mountains this is where the signal comes from.
The signal is best in South East Dublin, Sandyford, and bad in very built up Dublin city centre. The worst spots are probably between christ church and the liffey and the ground rises then falls. The centre of Dublin is at sea level, but it rises again on the North side.
It all depends on how far you are from the mast, and what is between you and the mast. In Sandyford a coathanger will work 100%, less so the further you travel.
My main gripe is the amount charged, and the fact the most expensive ones often work less well than much cheaper models.
It's a pity RTE's coverage checker does not show low, medium and high signal levels like some other countries coverage charts. I was even considering making such a map myself, as I have the software and data, but there arn't enough hours in the day.
Here is a sort of a map showing signal strengths for Dublin. Red is strongest, then yellow, then green, then blue. Grey suggests no signal. It not exactly based on RTE's broadcasts but is similar: