We stayed at O'Shawn's for three nights. The apartment is located at the basement level of a residential building. The inner yard doesn't look towards the street which is great and during the late evening it was very calm and romantic.
The apartment's location is top: just 5 minutes away from the Acropolis and Anafiotika, 10 min away from Phylopapus hill, maybe 12-15 min away from Plaka, and 20 min from Syntagma square. The area is very calm, there are restaurants, cafes, shops, bars, supermarkets, bakeries.
There is a self check-in, which is a good idea, and it's very easy. The place itself is spacious and modern, equipped with all the necessary amenities. It was very clean. Women would appreciate that there are an iron and a professional hairdryer provided. There is a flow boiler, which I personally don't enjoy for longer stays, but in our case it was not much of a problem. For longer stays you should better use the dryer, as laundry dies extremely slow due to the lower yard. During the day it gets very noisy due to construction and renovation work, but for tourists like us, it wasn't much of an issue.
At first, we were a bit disappointed that there was no internet during the first day and we had some work to complete with a deadline. And we didn't know about that in advance before booking. However, O'Shawn assured us that the connection will be working on the next day, which is indeed how it was.
We have had a great stay and I recommend the place for people, wishing to explore Athens' historical center!