Nutgrove Crescent, the settled Traveller development, is quite a bit away. It has been there for quite a while and there is very little trouble from the people that live there.
Having said that the parts of Marley that are accessed off the Grange road are considered to be a better area. This matters if you are into the whole snob value thing or if you are thinking of selling within a few years. If a short walk to a large park (St.Enda's) or a shopping centre (Nutgrove) and a school (Marley) matter then it's a good location. I'm not mad about the houses though.