Dina's Rooms are definitely a good choice if you plan to spend a holiday in Sifnos.

Dina is a nice Greek lady who rents a certain number of rooms in the beautiful village of Artemona. We paid 55 Euro (highest season, August) for a room that was very large, with two windows, A/C and fridge. The bathroom was brand new and with window! All furnitures were new and everything was extremely clean. It looked like it had been just renovated.
In front of the room there was a small garden, where we had our small table with two chairs, useful for spending some time outside.

Rooms are located very close to Artemona's centre, right above a large parking lot (the same of the Bus station), so the location is convenient either if you have a car, or if you rely on the bus service.