Went to Buenos Aires on 18th Dec 2011, and Casa Esmeralda definitely a choice if you are here. Located at Palermo, hub of good nightlife, very easy to get to the city, using bus number 111 or 93, or just few blocks away, you can get to the subte.
Staff like Sebastian and Cecelia and everyone is helpful, tell you about the events, get you updated if you ask them.
Decent breakfast! Owh yes, Dulce de Leche was great!
Argentinian style!
Room was good, the dorm room looks great! :)
Come to Casa Esmeralda!

Cheers!
Victor Druce

Very helpful and friendly staff. Sebastian, the owner, was very helpful, keeping everyone informed of any big event, shows, lessons, football matches, happening each week. Most of the double rooms were spacious (we stayed for almost a week and, having arrived without a booking, had to move around a bit, staying in almost all the rooms of Casa Esmeralda). Very clean (the cleaner would arrive every day at 11) and with a fabulous breakfast: media lunas and toasts, coffee, tea, fresh orange juice. Great common areas, fully equiped kitchen and a terrace with bbq area and views of Palermo (or the trees, rather).

We found it a bit far to get to the other main suburbs but once you get familiar with the underground system or have plenty of coins to use the bus, distance won't be a problem.

I stayed in a private room as I wanted to have good night sleep.
The room costs 150 pesos, I have paid 100 pesos more than the dorm.
There is an ensuite bathroom and toilet.
Everything was very basic. I stayed for a few days but the cleaner had never came in to clean or clear the bin once.
There were 3 private rooms at the back, and the rooms were separated by thin wooden walls.
My idea of having a good night sleep had been shattered by the thin wooden walls, unfortunately.
I could hear the woman next door coughing, and the couple shagging, I could even hear every single movement, eccckkk!
Then the cleaner comes in like 9.30am everyday started scrubbing on the sink right outside my room.
The breakfast arrangement was quite annoying. As we have to alert the staff at the front kitchen, shame there is only one staff in the morning who is not always there.
The breakfast portion is extremely small, 2 tiny winy toasts and 2 cheap tiny croissant with an espresso cup of fresh juice, plus free flow of tea and instant coffee.
That can hardly fill up anyone, especially we travellers need a lot of energy to walk around all day. Why not they just made it as the buffet style breakfast to let people help themselves like any other hostels?
The kitchen facility is appalling. The frying pan could hardly stand straight and the spatula were so tiny that it’s shouldn’t be called a spatula for cooking.
The internet is extremely slow, the computer is those last generation crappy PC, and the speakers and headphone didn’t work.
The Wi-Fi only works up to half part of the garden.
The good thing of Casa Esmeralda is the large garden and a lovely dog. Unfortunately I heard complaints from other travellers that the dog’s barks woke them up many times.
The location isn’t bad. It’s in the quiet part of Palermo Viejo, where there are lots of bars and restaurants. But not great for taking the metro/ underground, it’s about 15 mins walk away, not recommended for lone female travellers at night. There are lots of buses around, going to town isn’t a problem, but coming back is a real mission, as most roads in town are one way. I couldn’t find the bus where I got off to come back to the area again. I find the bus journey is pretty stressful, as all busses passe through the busy main road Santa Fe, it gets really dusty and chaotic, not a nice ride at all.
The staff are pretty laid back and friendly. But most of the time you cannot find anyone at the reception. I guessed you cannot expect much from a budget hostel.

We stayed here for 5 days this feb. The location was brilliant right next to the bars and restaurants. The staff couldn't have been more helpful. The garden was lovely and breakfasts very good. The only thing was the lack of air con as it was so hot while we were there.