Location is always most important and you'd struggle to beat this one. Just 30 seconds from the front door is the entrance to the Metro and an impressive new shopping mall. Also just 5 minutes walk to the river & 10 minutes walk to the Louvre.
The apartment itself is beautiful, put together with quality in mind, but characterful at the same time. We loved the small balcony where you could sit outside & eat breakfast. Also liked sitting out late at night in the cool air, as we were staying during a heat wave. Despite this heatwave the apartment temperature was fine; plenty of windows to open.
Olivier was a great host. Met us at start and end of visit, went though every detail we needed to know, even left us a welcome chilled bottle of water in the fridge!
Can't think of much negative to say. The shower head needed some attention but Olivier was aware of that. The floor boards can be creaky, perhaps an issue if you're moving round the apartment late at night and others sleep very lightly, but it is part of the character of the place.
Overall excellent and we'd definitely stay again if we visited Paris.