I stayed in Dublin three nights, two at Avalon House and one here. While it has a worse location than Avalon House, Isaacs has nicer facilities, and more comfortable rooms. If location near city center is not your number one priority when choosing a hostel, than Isaacs is a great choice. Indeed, even given its placement north of the river in the less touristy part of Dublin, it is not too far from O'Connell street and Trinity College, and it is right next to the bus station.
This hostel is great for any traveler. It is extremely safe, with a security team there at night and the rooms are clean and comfortable. What makes this hostel especially fun to stay at, is its young helpful staff, its good location near many pubs, clubs, and Eyre Square. Further, the hostel has many recreational areas with bean bag chairs, televisions, and spaces for socializing. This was one of my favorite hostels in Ireland, and is definitely worth stay especially if you are looking for fun.
This hostel was clean, comfortable, and the staff there was very helpful. The hostel is on the smaller side, and it feels almost like staying at someones home when you are there. The location is solid, a 20 minute walk from the Doolin Harbor and close to many pubs and restaurants. If you come to Doolin this hostel should absolutely be your number one choice.
While not especially nice, Avalon House is a solid hostel that provides you with a clean bed and a fantastic location for traveling around Dublin. While the hostel is a bit old and a little bit beaten up, it is still a place well worth spending a night or two at. I was particularly impressed with the four person room, which had two floors each with a two beds. This layout allowed my travel companion and I to have our space.