We had a great stay at Olivia's apartment. It had everything we needed and was nicely decorated and very clean. It is very small by U.S. standards but we only slept there, so it was no problem for us. The apartment is right across the street from the metro station but it is very quiet; many places to eat within 2-5 min walk, and a grocery store is across the street.
Although it may seem that it's located away from all the "attractions", we walked to Pantheon, then to Notre Dame within 1-1.5 hours and it was amazing because the city is beautiful and we discovered so many cute neighborhoods, churches, and University of Paris that we wouldn't otherwise if we took the metro. Many metro stations are within 12-15 min walk of each other, so don't think you have to ride the metro to go 1-2 stops.
Tip: Be prepared to walk, we found it to be the best way to discover the city (walked 33,000 steps per day :) ). And buy tickets to major attractions in advance through their websites so you can skip the lines.
The apartment has no windows or air conditioning and it's almost at the basement level so it gets very stale and humid inside. We visited at the end of October (highly recommended) and it was OK. We had to keep the door open to air out the place at night. I can't imagine what it'd be like in the summer when it's hot. It has a fan, but it may not be enough.
Pay attention to the check-in instructions. You'll have to pick up the keys at one place, then walk/ride the metro to the apartment.
Tip: Figure out your mobile connection before you come to the city. Wi-fi is not readily available to the public so you may end up without data. We signed up for eSIM which gave us unlimited data for 5 days, it worked well.