Nice apartment, good for two couples who want privacy as there are two separate rooms with their own entrance and lock, washroom, kitchen space. The smaller room faces the street and has blackout curtains so no problems sleeping, while the other room is larger but you hear more of your neighbours. The best part of the stay is how responsive Niko and Nelly are and they provide great tips and they organized 4 airport transfers for us (we all arrived and left at different times).
The one thing I would be cautious of is that those who don't have much experience travelling or have only been to clean, pristine, organized cities, then this neighborhood may be a bit rough for you. Nothing will happen to you but you might feel a bit anxious about going in and out of the flat especially in the evening. There are some homeless people, youth and/or migrants appear to congregate in an area in a square half a block from the apartment. You can avoid them though if you always return to the flat from the street with the police station. Otherwise, the location is very close to the Omonia metro station and a handful of bakeries on the way there for a great breakfast or lunch. Overall I would stay hear again as it is quite good value and the hosts are very responsive.