There is a very good thread on this in the Transport/Commuting forum on
www.boards.ie. All the pros and cons you could wish for on the issue.
Personally speaking, based on where I live now, it'll be 2015 (when the interconnector is built) before I see any benefits.
It's good to see other areas of Dublin having access to rail/LUAS/metro/whatever, and the commuters in Navan and Cork. The West? Time will tell. Hopefully the Ennis/Claremorris link will benefit the towns it runs through, but I would be sceptical (I'm not trying to deny the West a fair shake here, I just don't know what would attract people to Claremorris????).
As has been pointed out, the Dublin plan still misses out areas like Rathfarnham/Templeogue/Terenure and also Finglas.
The IE ads at the moment make me sick (Double the number of passengers etc. Ronnie Drew's stupid mug all over the place). I use the DART twice a day, 5 days a week, and different time each day. I have yet to experience the wonderous 8 carriage DARTs, and congestion is as bad as ever. Roll on 2015 (when I'm sure that any improvements will have been overtaken by population growth?)