Amazing location - you can't beat it as it's ideally located and so close to the Louvre and walk across the river to Saint Germain to the south, north to Sacre Couer/Montmartre to the north, east to the Marais or west to Champs Elysée!
The flat is indeed small though, but as we were there to enjoy the city it didn't matter to us. It is clean and simple, although as others mention the ceiling is very low -probably only 6'1" so at 5'10" I felt like a giant and still felt I had to stoop. This is even more apparent with the shower as you have to step in and up into the bath, so I pretty much had to sit/kneel or bend over completely to wash and rinse.
But the location cannot be beat and we would consider staying here again on our next visit!