It's quite OK Value for the price. The area is very nice and you find lots of cafe's bars and restaurants. The Metro is very close and it's easy to navigate your way to the various touristic and historic places in Athens. Actually the acropolis is basically just up the hill. A 20 - 30 minute walk through the park. Which also gives you a splendid view over the city of Athens.
The flat is in the basement of the house and not very light. Everything is clean and works, but everything it is all a bit shabby and used. However, OK value for price.
The owners are very friendly and helpful. The kitchen is OK, but I rather went out to eat. There is AC and an extra heater (That area of Athens is quite inexpensive)
All in all I enjoyed my stay in Petralona a lot. I come back for sure