Best thing about this place is the location. No doubt about it. Right in the middle of Plaka. You can't really get better...
But other than that and for a price as low as it is, don't expect anything extraordinary !
The flat is clean enough but feels a bit congested with a lot of stuffs inside. Sens of decoration is inexistent. A/C is not very effective even when pushed to the maximum, which can be a problem during heat wave in Athens. TVs are out of order. Wifi speed is barely ok. Kitchen and bathroom are very very basic, to say the least...
Terrasse is ok, but you have to be aware that it's kind of shared with neighbours. The rooftop access within the next building is a very good addition though (but also shared with neighbours, of course)
Otherwise, Deni & Geri (and Sotiri who is in charge of the building) are very helpful and nice. They allowed me to leave my luggage in another room next door because I had a very late plane, which was super kind and sweet.
So overall, it's a rudimentary place with a great location and nice owners.
From my opinion, it could be a good fit for anyone looking for a cheap stay of one or two days in Athens (which was the case for me, returning from islands before taking my plane back home)