We spent two nights at the Athinaiko which we found to be basic but clean and centrally located. It's within walking distance of the port and the archeological museum. Staff was very friendly and helpful. Very good value for 50 Euros per night. The rooms are large with fridge, AC and lots of hot water. It's right on a main street so the traffic noise may bother some light sleepers. Our room also had a balcony with two chairs and a small table. Wireless internet access was a bit spotty at times.

The hotel is good enough, we chose it for a one-night stay for its location and reasonable price. It's really very close to the port (walking distance) and not far from airport. Good for those who needs stay between plane and ferry to Santorini as we did.
The staff was very helpful and friendly, clean room, good breakfast and Internet access included what was extremely good for us to find some info for our further trip! Cozy shady place near the hotel for a small rest. We liked very much the design of breakfast room for its nice sideboard with family photos and kitchenware! A little bit noisy from the street but with closed balcony it's not a problem.
So I would say - no frills and all necessary for its value. Nice place :)