Maria and Anna's place is perfectly situated about a 20 minute walk from Fira, away from the hustle and bustle, but be prepared that in the off season when many restaurants and shops are closed, it's harder to find places to eat. It was really easy to get there from the ferry port, though! I just took the bus from the port(2.30 EUR), asked for the Karterados stop as Maria and Anna had indicated, and then walked from the bus stop approximately 800m. The sign was very visible and you can't miss it.
The room itself is very spacious, and since it was winter I appreciated that the room was heated and the heater worked very well! There were also extra blankets, and both the hot water in the shower and the water pressure were fantastic. I had everything I needed, although I would've loved to have a tea kettle in the room since I'd brought my own tea bags and instant coffee, and there wasn't a coffee shop "just around the corner" as I'd hoped. Overall, an unbeatable value to stay on the beautiful island of Santorini.