We had a great stay ! The place is lovely, in the center of Athens and the neighbourhood is very nice. The kitchen is quite small but we didn't need it thanks to the amazing offer of cheap food in Athens (although we might have cooked more if it was a bit more practical).
As said in other comments the sound-proofing isn't the best, but the street sound is not unbearable, even on weekend nights, at least in our opinion. However we suffered a lot from the sound our neighbour made as he was making noise until very late, there was a lot of passing in the hall with people constantly banging on the hall door which you can hear very loud from the apartment. But anyway this was the only negative aspect of our stay, and I guess we just weren't lucky with our neighbour (which is also an Airbnb if I'm correct, so you shouldn't worry about it).