Our stay in the Caroline&Eric's house have been very productive and stimulating. We didn't know them in person, but the communication have been regular by mail and very fluent. Despite of a little problem the first night (Eric was very kind with this issue), the next days were wonderful in the flat. The kitchen has everything: fridge, freezer, washing machine, heat plates, one Nespresso machine,... maybe we miss a microwave, but the heat was enough.
The rest of the house is fully equipped: bathroom with toilet and bath, dining room with sofa, a large screen and sound equipment; bedroom with king size bed (there is no blinds in the rooms, but there are pretty blackout courtains)
Regarding the zone in which the flat is located, is closer to the Pigalle metro station (500m). The Sacre Coeur is about 15 minutes walking and Louvre around 35 minutes walking down the street Rue Martyrs to the end (but the best choice is the Metro, no doubt), and for the bold people, the Moulin Rouge is about 10 minutes walking ;-).
Definitely, it was a great place to stay more than a week (the worst part: so many stairs to climb to the 5th floor. The best of the worst part: you do fitness free and your legs are stronger everyday :-))