I'm living in Kilmainham, past the gaol and the Hilton, since last September, and love the area. As you say, near to town, I walk in and out to work every day in 40 minutes, yet having IMMA, Memorial Gardens, the Liffey and Phoenix Park so near, you feel like you are out of the hustle and bustle.
Down in Old Kilmainham is a bit more industrial, but feels really historical and grounded. Seems like a lovely part. Some great pubs nearby too, but no decent restaurants around at all unfortunately. Lacks the village buzz of other suburbs close to the city.
Have seen no trouble since i moved in. Seems to be lot quieter and nicer than all the surrounding areas like Rialto, Inchicore, Drimnagh, Islandbridge. Not being snobby, but think the lack of big blocks of corporation flats helps. But as a result, you will pay a bit more for a Kilmainham address than for a neighbouring one.
"They" say Kilmainham is full of artists, actors, musicians, etc. but I've yet to see much of that about the place...although if I frequented the Patriots Inn and the Royal Oak a bit more, then maybe I would!!