Couldn't recommend Irene's place enough! She's an excellent host and the room is amazing.
The place is located in a quiet and scenic part of Sifnos, with great view overlooking the picturesque village of Kastro (a must visit, along with eating at 'Loggia' tavern at the edge of the Kastro). The rooms have been recently renovated and have a distinct Cycladic feeling. Parking is very easy too.
Irene has given us extensive help on which beaches and restaurants to visit - and we had amazing food at all recommended places. She also ensured that the place was very clean and promptly catered for all our ad hoc requests.
Tip: Irene's family makes this amazing Sifnean hard cheese called 'manoura' (among other traditional products) - ask her if you can buy any, it's incredible!