We spent a weekend in September here as a couple. The positives: Checking in/out was straightforward, the air-con works well, and the location is great - just a short walk from Kerameikos metro station (direct connection to airport) and the busy surrounding neighborhood. The apartment was also mostly clean (floors, appliances, etc).
Sadly, the rest was disappointing: The place is worn down and not cozy. It is pretty dark (mostly just ceiling lamps) and the mosquito nets on all windows are broken (lots of mosquitoes in front of the front door and plenty inside when we arrived). The kitchen is very poorly equipped (e.g. no spatula, no small spoons, no regular knives even, only one huge pot). The ‘couch’ is two single beds with some pillows, not comfortable. The bed was also not comfortable to us (metal-spring mattresses that have seen better days). Unlike what the photos are showing, there are no carpets.
The place could be made nice again quite easily (add some nice lamps, fix what is broken, replace some furniture) but the way it is now is disappointing.