The Citi Hostel, located in what we'd call "Central Dublin," is at least a 10-minute walk to most of the sites in South-of-the-Liffey -- making it a bit off the beaten path. But because of this, you'll get to experience the real Dubliner environment when walking "home." And, the Harcourt Street tram stop is just a few blocks away, so you can easily get to other places.
Citi is comprised of two connected buildings - the older East Wing and the newer West Wing. Each "wing" comes with its own kitchen and common areas. A wide array of room options abound, from en suite twins to 14-bed dorms. All the beds are bunk, dressed in fluffy duvets and sheets. Smoking is banned in all of Ireland's hostels, but you can light up if need be in a sunny area between the wings. We highly suggest staying in the West Wing whose tidy tiled toilets, stainless steel kitchen appliances and Ikea-esque furniture give it a cleaner, sleeker feel.
Note: the hostel offers weekly rates therefore attracting not only backpackers, but also people who want to work in the city.