We had a great four night stay at Stelios in June. Chek-in was a breeze. We were running late from our drive back from Delphi and Stelio was in constant contact. The street was a little hard to find for our Uber Driver, but Stelios was waiting in the street for us (for a late night check-in). He even helped us carry our baggage up as we had a baby and ton of things.
The street is covered in graffiti (and so is most of Athens), so I was a bit skeptical when we first arrived. The building itself is mostly empty, so that may put you off at first as well. But once we entered the apartment, we were pleasantly surprised at how big it was. There were fresh sheets and linens (the sheets smelled amazing) and place was really clean. Wi-fi was great as well.
The location of the apartment can't be beat. You can walk to everything and the street itself has this cool circus theme restaurant that was quiet an attraction at night.
My only complain was that it was a little loud at night in the room that was facing the restaurant next door when they had music nights. But we just slept in the other room that night and we were fine.