Stayed here for four nights with some friends, and would definitely recommend this place, particularly for younger people / groups looking to explore all that Berlin has to offer...
PROS
1) Location - In the heart of Friedrichsain (a cool neighbourhood, formerly East Berlin), very close to everything you'll need (cheap groceries and beer directly across the street, local restaurants bars and cafes in abundance, easy bike rentals nearby, nice leafy parks, etc...). The Ostkreuz transit line is also only a 5 minute walk away and directly connects to both the airport (Schönefeld) and city centre (incredibly easy to get to / leave).
2) Price - very reasonable, especially with a group of friends contributing (as long as you're happy to share a room...)
3) The balconies - one overlooks a nice little park which was perfect as the weather was ideal, and the other overlooks a fairly busy road.
4) Surprisingly spacious living room with two very sleepable couches
5) Fully stocked kitchen with all the (basic) appliances
6) The building - quiet and safe during our stay.
CONS:
1) Have to pay 10 euros (?per device) to use a local wifi hotspot. We opted not to.
2) Additional fee of 10 euros per person if you want towels and linens. Comfortable, yes, but annoying.
3) One bathroom for up to 6 people...
4) Only one key for all of us as well.
That being said, overall was very pleased with the place as our little hub for exploring Berlin and would happily go back!