We thought the location of Naxos Diamond Apartments was excellent; close to restaurants and about 10 minutes walk to the port. There is also a free parking lot 100m away since you should rent a car on Naxos.
There are 7 apartments managed by Antonis and family and it has the feel of a small hotel with daily room cleaning and fresh linens and towels every other day. The studio was kept exceptionally clean.
A couple of notes are that there is a private little terrace but no indoor seating. Also the terrace is slightly below ground level so you cannot see the street while seated. It may be worth choosing a studio on the second level in order to have a balcony if that is important to you.
There are two beds in the studio, a double and a twin. The twin was slightly less firm.