Pros: Olga was very helpful throughout the process, and even put in an A/C in the main room as that was a key concern for me. The location in Apollonia is also very good - near shops, restaurants, markets and bus stops to any beach within minutes. Sifnos is itself a really amazing island and our favorite so far in Greece. Amazing food as well.
Cons: Two major negatives greatly impacted our stay, unfortunately. First, the description says 2 bedrooms, so my expectation was 2 enclosed rooms. However the main bedroom is actually open - i.e. no doors from the stairs, and therefore no privacy. The only enclosed room is a small room that is about 8ftX8ft with 2 single beds or a double. It was very challenging for our 2 families to share this space and I would not have taken it if this was clear. I looked everywhere in Airbnb for "bedroom" definitions and couldn't find this. I will assume this was NOT intentional on Olga's part and hope that she re-does her listing to be more clear - but as much my fault for not even thinking about it and lesson learned for me. The second major negative was a major mosquito issue. Olga provided one electric plug-in repellent with tablets, but we had no idea the extent of it. About 50+ mosquitos regularly on the ceiling of the inner living room and all bathrooms - the young kids were bitten well over 50 times on our few days, mostly on their face :(. 2 windows that provided breeze in the living room had no screens, while others did. Even when we did close those, mosquitos found their way in. We bought additional repellent coils etc but to no avail - it was really rough. I've traveled to over 50 countries, many tropical with major mosquitos, and so I know there are good solutions for this.
In addition to this general upkeep of the bathrooms was not great. My expectations were reasonably high for spending just under $500 per night USD for four nights. I believe these issues are within the possibility to fix, which would then make this place much better.
Wishing Olga the best in building her business and hope the feedback is helpful to her and to future guests.