Lovely place, worth the money. There is quite a bit of noise from the street (including in the evening as Athens is a rather vibrant city), but if noise doesn't both you or you're out and about making it too, this is an absolutely wonderful place. It is quite secure with a gate to come in at night, plus the door to the apartment building, then another for your own door. The floor also seems to only be Airbnb apartments, thus making it a nice environment to meet fellow visitors.
Also, avoid leaving the windows open because the mosquitoes WILL get you and the apartment is spacious enough that you'll be hunting them for a few days.