We spent a week in Claudia's Rue Mouffetard apartment and thoroughly enjoyed our stay. We were four adults and found the apartment to be large by Paris standards and very charming. While one bathroom was quite small, having 2 bathrooms was very convenient. The kitchen was small but functional for preparing breakfasts and snacks each day.
The beds were comfortable and there was plenty of hot water for all of us to have showers each day.
The area was very interesting and close to all amenities - supermarket, cheese shops, bakeries, wine shops, fishmongers - you name it, rue Mouffetard had it. It was also close to the Metro which made it easy to sightsee.
The advantages of the neighborhood however, also meant that it could be noisy at times. The apartment faces the street and you can hear the revellers as the leave the bars at night and the merchants as they set up their market stalls early in the morning but for me that all contributed to the charm.