I know a little about Dublin 15 as I have some friends who live over there, I also at one point put a deposit down on a house in Tyrellstown - about 8 years ago - but didn't go ahead with it.
I think you need to be very careful as there are alot of good, bad and ugly neighborhoods within the post code.
If I was buying there now I would look for the following:
- A development built before 1998. Alot of developments built in the last ten years were sold to investors and tend to be ageing badly. Also, alot of property in the Dublin 15 area was included in the social and affordable housing schemes, which can sometimes have its downsides.
- A development which is on / near the Maynooth train line. While the road infrastructure there has improved greatly over the years, there's still alot of bottlenecks when commuting (like everywhere).
You don't say what you're hoping to get for your budget - a house which meets the criteria above might be hard to find on your budget.
Remember there is plenty of supply out there, so bargain hard.
Best of luck!