other than people who live close to the stations and their jobs are very near the stops on the limited routes, i cant see it having any effect on the chronic traffic problems in dublin.i.e. people will still drive their cars to work.
people as a rule dont like walking that much (especially on a daily basis) and you have to pay a fee for park and ride so if anything it will be worse.
i personally think its a white elephant (and a very expensive one at that!!)