Fantasia Apartment is a really lovely place to stay. The location was perfect for me - away from the city in a quiet area, but still close enough to walk (35 minutes, or there's a free shuttle bus from the bottom of the hill). The view from the rooftop is fantastic too, day and night, over the sea and Ermoupoli.
The apartment itself is very stylish, and you can tell a lot of thought has gone into it. Sitting on a deckchair in the sun in the morning is just wonderful. Even in winter, there were plenty of warm sunny days. (And some fantastic lightning storms.) The kitchen is well equipped for cooking anything you can think of. The bed and sofa are really comfortable, and the TV can connect to Netflix and Youtube. I had some great lazy rainy days.
Wonderful hospitality from Ippokratis, who picked me up from the port on my arrival and welcomed me with spanakopita and bread. We had great communication throughout my one month stay. When there were (unavoidable, weather-related) problems with the wifi, Ippokratis was always available to solve things as quickly as possible, even remotely from Athens.
Some days I was a little cold, when the weather was grey and it's humid, but Ippokratis bought me an extra heater, and eventually the built-in aircon heater warmed the place anyway. I think this means in the summer, it will keep the heat out very well. Sometimes the kitchen and bathroom were damp from the humidity, but I think this is only going to be a problem in winter too.
There is also sometimes a friendly cat :)
I will miss laid-back island life on Syros, I hope I can visit again!