The stay at Vassiliki's was great, this has to be the best value-for-money-place. We came during the off-season (late october) and as the weather was still warm-ish we had a great time at the Kamari beach which is just 2 minutes away. We also enjoyed the breakfast at the close-by bakery, which has great pastries, sandwiches and good coffee.
To explore the island, we mostly had to take the bus to Fira to travel from there on, which was no problem for us, as we like to use public transport and the bus went every 30 minutes (1,60€/Person).
The place itself was clean and a bit bigger than anticipated from the pictures. The balcony of our studio had the view of the sea and during October you can see the sunrise from it as well.
Vassilki, the cleaning staff and the airport pickup (organized by Vassiliki, 20€ additional cost) was very warm and the room was cleaned every day. Vassiliki briefed us well on everything and helped us also in planning our time in Santorini with great suggestions and booked the boat tour for us.
Would definitely come back again!