Marc & Rumi's place was great for us (2 grandparents of 56 and 62 years). It is very close to the Eiffel Tower, the river, the RER rail station, and the Invalides metro station. We walked most places. The furthest place, Notre Dame, was about 45 minutes walk. The Louvre and the Musee D'orsay are about 20 minutes. There are lots of cafe's nearby, and a good bakery, as well as three grocery stores.
The room itself has been very cleverly designed, with a table for eating or using the computer, a couch (which doubles as a single bed), TV, internet, and a small closet. The bed pulls down from above you and sits at about chest height. You use a small stool of two steps to get into it. When it is down, it pretty much fills the room, except for the couch. I'm 6'1" (185cm) and had no trouble getting in or out.
There is not much of a view, just a few trees in the space between buildings. But we went to Paris to see the sights, not to sit in a room. Even so, if you did want to spend time in the room, it is very comfortable.
We really appreciated the drivers they offer you. And there is someone there to meet you at the flat and show you how everything works.
We would definitely stay again.