I stayed at TJ's for just a weekend but it was really good. Although the place is quite small, there's everything you need for a few days, it's close to the city center (about 15 min on foot) and everything else (coffee shops, bars, restaurants) is nearby. I've really appreciated the bus stop 20 meters away from the room. It was very convenient, especially for bus 16 which directly goes to the airport.
Plus TJ is a really nice and friendly host. Both checkin and checkout went smoothly.
I definitely recommend this place if you're planning to visit Dublin :)