The apartment has a great view over Platis Gialos, it's like in the pictures.
The apartment is fairly small but it has everything you need to spend a week in Sifnos, especially for 1-2 persons. It includes a small kitchen where you can prepare some meals, such as breakfast (but less to cook meals, really, as it's small).
The apartment was clean and the cleaner came over every other day. WiFi worked without any issues during the stay. The owner reached out fast when a couple of things were needed for the kitchen. It's up on the hills so it can get windy.
A car is definitely recommended. The road towards the apartment, the off the main road small part, isn't really that bad if you're used to the roads on Greek islands but pay attention to the sides.