Old Quarter = Not worth it. This place is only a few years old and looks run-down already. The density is far too high there - you get a smell of trash all around the place almost something you'd think of in a estate of student accomodation. Also, since so many of the houses have no back garden access peoples front gardens are littered with bikes, bins, etc that really brings down the look of the place. To me, it seems obvious the builders built this place for people to buy off the plans and rent to first suckers to come along. Rented there for a while - see no positives at all to this place.
Lisheen Fields = not worth it. Although I don't have first hand experience of living there, I can tell just by the look of the place it wouldn't be suitable for families. For one, yes all the houses are detached but they are so close as you look up between the two buildings you feel like you're in a cave. Also, a 3 story house is suitable for families at all, you'd have stair gates everywhere and once a child is on another floor they are quite far from you, more than just in the next room. My guess is either that none of the houses are built with play room and the other normal stuff families need to function.
Classes Lake = solid choice. Although this place is massive, the houses were built before the builders went off their heads building any kind of junk. The houses have utility rooms, play rooms, decent gardens (front and back) and usually enough driveway to park two cars although some streets clog up with on street parking.