I'm from D8 originally and work there (James's Street) D8 is a big place so there are more run down places and some really good ones. I'd walk a lot and have never any trouble. Good pubs, one of the best chippers in Dublin (Macari's near the Black Horse) a new place in Kilmainham Cross called Union 8 seems pricy but I've heard good things about it.
I get the 40/13 regularly . They are pretty good. Depending on where you are you could be close to the N4, that route is really good, 79's and others a little faster into the city in rush hour. But on the 40/13 route It will get from Inchicore to Dame Street in about 30 minutes at rush hour, sometimes 20. There is a nice community feel in Inchicore village, very settled.