We stayed here for 5 nights, and enjoyed our stay. The place is clean and had the basic facilities you would expect. The check in process was smooth and we liked the neighbourhood (although it isnt pretty might seem shady, it's actually pretty fun to be in).
Two downsides: the bed was not very comfortable (too soft, you could feel the springs) and the water pressure in the shower was pretty low. But this did not ruin our stay at all.
We can recommend staying here if you choose to be in Athens for half a week. For a longer stay i would prefer a place with some more sunlight and space.