I used to live in Ongar, only moved out recently. Glad to be out of the place to be honest. Ill give you the plus points as well as the minus to avoid being completely negative
Good:
Good location, short drive from Blanchardstown, near the train & bus making it accessible to town as well as all of Dublin 15
Good facilities in Ongar Village, which is walking distance from pretty much all of the houses
Good public transport-buses, train
Bad:
Build quality isnt great, soundproofing is awful ( we could hear neighbours running a tap or using the toilet!)
In some parts it feels very cramped as though houses are built right on top of each other.
Lots of cars in our area got broken into-although Im told that this is a problem in many new estates
Ongar is covered by Lucan Garda station rather than Blanchardstown, they can often take quite a while to call out if you report anything. We had a few bad experiences where no one came out at all
We noticed a lot of kids started hanging round int the evenings/at night, either on the green areas, in the car parks or even at one stage in the hall of our apartment building!
In our area there were few owner occupiers, in fact most of the tenants were social welfare. Some were lovely but a lot had very little respect for the area.
Although the public transport looks good in theory-I found the 39 bus pretty useless as it took about 90 minutes to get into town at peak times, and although the train service is quite good its a 30 minute walk from most parts of Ongar, and as others have said its pretty packed most of the time!
Don't want to go too much into the specifics, but if anyone wants more details feel free to PM me