My friend and I stayed at Marlborough early February for two nights. We found the reception to be a little on the cold side, they could have been a little bit more welcoming.
Once inside, the lounge is inviting but you would not spend your nights there. There is free Wi-Fi available in lounge area only, and computers with a connection are available at a small fee. They are, however, located in a freezing part of the hostel. Bring a jacket.
The rooms are basic, but there is locked storage under all beds, which comes in handy. Reception provides a lock and key for you upon arrival.
Toilets are clean, showers are clean BUT, due to the push button system, you can not control the temperature and at the time of our visit, it was scorching hot and you could not shower for fear of burning you skin (mine was all red after a short time and I had to step out).
Location is very good; located one block from O'Connell Street. Look for a church and it's next door. You will have to ring to gain entrance, and it might take a few minutes if reception people are away from their desk. Keep ringing. Ten minutes walk to Temple Bar area.