I stayed at Alix's lovely studio for two and a half months (!!) for a summer internship I had in Paris. Here are the key points to know/consider about this flat:
1. Alix is a great host, everything you would expect and more. For example, I wanted to bring in a cleaning lady once a week during my stay (and I don't speak a word of French) so she took care of the whole thing and I only needed to leave money on the table for the cleaner. She even helped me to get a mobile phone line and was extremely helpful in every aspect.
2. The apartment is newly renovated. It is great. The shower works perfectly and there is heating. You will not have "issues" with this studio flat.
3. The flat is perfect for a single/couple but might be slightly small with a baby (but this can be done as well).
4. The street is quite noisy and crowded with bars/clubs. You are literally in the middle of the action. However, the flat is generally quiet (although there is the occasional noisy night). If you are looking for a "cool" place to stay, this apartment is for you 100%.
5. Transportation to and from the apartment (from Gard Du Nord etc.) is great, plenty of routes.

Basically, this is a great apartment with a great host and at a cool location.