I only stayed for a very short while, on a layover in Athens, but I liked it so much that I really wished I had stayed longer. Reception is open throughout the night and checking in and out was no problem at all.
The hotel is centrally located, very easy to reach from Syntagma square if you just follow the streets to Monastiraki. It's true that the houses around it are very run down and the walls covered in graffiti, you'd think it's dangerous, but I walked by myself at both 2 and 5 in the morning and felt perfectly safe, because it's so close to areas where there are restaurants and crowds.
It's got modern decor, it's very clean and comfortable. The shower was great, hot water with great pressure and towels and toiletries provided. The view from my room was not particularly inspiring, but on a budget and on the first floor in the neighborhood it's bound to happen that you get the shaft, besides you're not there to spend time in the room. It was also very quiet, I didn't hear anyone else or any noise coming from the other rooms.
Internet worked perfectly, there was a TV in the room and air conditioning.
I didn't have the time to eat breakfast or check the view from the rooftop terrace, it's closed at night, but judging from the location, I do believe it's great.
Not suited for a layover, but for a longer stay in Athens I could definitely recommend this and I'm looking forward to going back, I was very pleasantly surprised by it and the lively area of Monastiraki.