Martine & Sebastian have a beautiful and very cool space that blends traditional Santorini style with modern features.
They are extremely helpful hosts, going above and beyond (Sebastian even drove us back to the airport when the airline found our lost baggage). They have great suggestions for things to see on the island.
While Santorini isn't huge, the house is located somewhat outside of the classic tourist spots on the North End of the island, so I'd recommend renting a car if you can (since the bus trip up to Oia can be a bit tricky, especially in tourist season).