Highly recommend staying at Kosta's apartments! We stayed at the "Astra Apartments." Kosta and his mom, Heike, were there to welcome us when we arrived and we felt very taken care of. A bottle of orange juice and a bottle of Coke were waiting for us too! Kosta always responded VERY promptly, when there was no hot water at 10:30 at night he fixed it immediately, and when I broke the shower hose he had it fixed ASAP!
The apartment was very nice with many extras, marble floors, newly-tiled bathroom with new toilet and sink, nice little kitchen with fridge and stove, cups, plates, cooking utensils, etc. The bed was a little hard, but not too bad. Nice, soft lighting. The apartment was cleaned every single day which was a REALLY nice bonus and pleasant surprise! Beds made, new sheets and towels, floors mopped, bathroom cleaned---even our dishes were done although we did not expect that! We also had full use of the gorgeous rooftop terrace upstairs. The daily cleaning alone was worth staying in this place. It was so nice to come back each day to a nice, clean apartment.
The location CANNOT BE BEAT, you are less than a one-minute walk to Agios Prokopios beach and there are two small grocery stores that are a 30-second walk in either direction and plenty of restaurants, too.
In mid-May when we stayed there were not many people around so we really had the place to ourselves! Keep in mind however it is about a 15-minute drive or a 5.5 kilometer/3.4 mile walk or bike ride into Naxos town itself, so you are a little further removed from the shopping/restaurants/harbor of Naxos town itself. There are still plenty of things to to in Agios Prokopios though and it was nice to be in a quieter setting.
Thank you Kosta and Heike for a great stay, we loved it!