In general, considering the price, this house is totally worth it, especially for the great location, but you should consider some aspects before booking.
Pros - the apartment is in a perfect location to visit the main turistic spots of Athens by foot (we never needed the metro!). Perfect communication, Konstantinos replied to us every time in a matter of minutes. The bed was comfortable.
Cons - it is situated in a VERY NOISY area, with a main road busy all the day and night, and you can hear all that, the windows do not isolate the sounds at all. So, if you are a light sleeper, I strongly suggest to find another place (I usually sleep everywhere without any problems, but this time it was a bit too much even for me, fortunately I was so tired that I slept anyway!). The apartment is a bit smaller than it seems in the photos, especially the bathroom, and the kitchen is very limited, so it's okay if you don't plan on eating at home (there isn't a table to properly eat). The building is very very old, without a lift. The balcony is on the main road so not a very nice view.