15 minutes walk from Dun Laoghaire Dart station gives a fairly large area. I've just moved out of Monkstown which I really liked and which was about a 15 minute walk to DL Dart Station, though closer obviously to Salthill/Monkstown Dart station.
There are some really nice spots in DL and some not so nice areas. The upsides are that you've got pretty good shopping, pubs and restaurants within walking distance and of course the piers and the sea and you've great public transport options - 46a is a great bus service as well as the DART. Downsides would be that in my opinion the main streets are pretty grotty and dirty looking, some of the flats (in converted old houses) can be grim and it's probably a bit over-priced still.
Are you looking to rent a house or an apartment? What specific info are you looking for?