Claire's flat was great for us. A comfortable living room for relaxing at the end of the day and planning the next days outings. Convenient for many places we wanted to get to (Cite de la Musique, the Marais, public transport, local shops and restaurants). We recommend Scaria restaurant nearby. We usually stay on the Left Bank but would happily stay in 11th again.
Other positives - quiet, good heating and shower, comfy sofa (unusual in our experience), separate toilet.
Could be improved - typed instructions for arrival and departure (recycling, rubbish?) and local information. Better (and more) pillows, enough proper bath towels. Kitchen - we didn't do any cooking apart from breakfast but small changes (eg wine glasses, a step to reach high cupboards) would have been useful.
We found the 56 bus easier than the metro to get to the gare du nord with luggage. We used the Citymapper app loads and it would be helpful to anyone unfamiliar with the area or public transport (it included info about changes/closures due to strikes during our stay).