I stayed at Ermou 51 with my 2 teenagers for 3 nights in June. We really enjoyed our stay and would stay at the same place if we come back to Athens.
The studio is spacious and very well designed including the bathroom. The bed and sofas are very comfortable and the kitchen is simply but well equipped. There is also a washing machine with detergent provided.
What we appreciated the most was the location: in a car free street, in the heart of Athens, all main monuments or sites are walking distance, a great selection of restaurants in the welcome guide all within 10mns walk.
Kudos to the Up-Street team that was very responsive and helped us throughout our stay for any small queries we had.
Worth mentioning that you can hear the street animation (music mainly) at night but it stops around 11pm. But