We've stayed in quite a few Airbnb apartments now, and the Poseidon room at Enosis is definitely one of two best places we've booked! The inside of the room was nice, but the view from the amazing balcony couldn't be beat! Agia Anna is a little village right on the beach, about 15 minutes south of Choros, the capital and where the port is. We were driven to the hotel for free, which was great.
Unfortunately, our vacation was apparently just before tourist season, so most things were still closed, or preparing to open -- restaurants, supermarkets, even rental places. This certainly isn't the fault of the host, though. We were told if we had arrived a week later, everything would probably be open. On the flipside of that, all the beaches were practically empty! Plaka beach, listed as one of Greece's top beaches on several travel websites, had possibly 10 people. It may have only been the last week of April, but the water was beautiful, and essentially warm enough to swim in (I did.)
Basically, you should absolutely stay in this hotel if you can, but do it after May when everything is open, and rent a car so you can explore the rest of Naxos!