Ronald's place is a cozy spot in an incredible location close to metro and a lot of the tourist destinations.
I stayed for 2 nights and found it to be exactly what I was looking for. The bed was a very comfortable twin and I slept well. I used the kitchenette with ease to cook my own meals (though I'd recommend getting a frying pan). The bathroom was clean and the shower had good water pressure - I was provided with soap and towels so I didn't need to use my own. It's definitely a small studio, but it's very comfortable. You can get a nice view out the window if you look!
Ronald himself offered a lot of great recommendations for museums beyond the typical Louvre and destinations other than the Eiffel Tower, which was much appreciated!
Small notes: You have to climb a fair amount of stairs to get to the apartment which I liked because I thought they were beautiful. There was construction in the square outside the apartment but it didn't start until after I was awake.