Maria's house was a wonderful spot for us. It was very close and walkable to all the shops and restaurants in Oia and it was quaint and cozy with a gorgeous view. She has a team of people who help her out who are all absolutely wonderful. They coordinated our adventures, offered advice and gave us tips from locals that really made our trip amazing.
The only negative thing I could say about this is that to get to the house you have to take the main path to the castle which hoards of people are walking to watch the sunset. If you get caught at the wrong time of day you can get stuck in crowds of people making it hard to get to the path to the house. We just solved this by drinking an extra glass of wine and avoiding this area around sunset because as soon as the sun goes down it is so quite and wonderful.