agreed on the landtax first off.Firstly can the debate about land taxes etc start a new thread if required ,off topic arguments do nothing for the thread except clog it up.
Secondly considering rents are lower now than 6 years ago can you imagine the case if immigrants were'nt arriving by the planeload!! rents would be even lower and prices may have already corrected. The EU accesion in 2004 gave the market an extra push, albeit short term. Apartments coming on stream all over Dublin, cant see rents going much higher in real terms, recent investors must be starting to feel the pinch of the rate rises,give them another year and low/zero/negative capital appreciation and they'll be rushing to exit the market.
secondly, another contributor to shoring up rents, certainly in parts of Dublin are the HSE rent payments. In parts of Dublin, that exceeds market rent for a lot of properties.
That being said, I would expect that the rental market will take a brief hammering as people try to cash in on their investment properties, particularly if they are subsidising rents.