Me and my girlfriend spent an absolutely great week in Cinderella's studio at the beginning of June. Yes, the flat is tiny, but the space is arranged very ergonomically, and you will find everything you need there (just check out the drawers and you will find treasures like an extension cord or a knitting kit). We also loved the taste with which the studio has been furhished - even things like dishes were beautiful and fitted the atmosphere of the place perfectly. It is very romatnic too! - especially with views of Parisian roofs in candle light. :) The only downside may be the fact that since it is a flat situated directly under the building's roof, it is quite susceptible to temperatures, so on hot and sunny days it becomes very warm. But then again you have got a fan which is very useful on such occasions. We also appreciated a very large and comfortable bed, as well as the access to Internet and the presence of a laptop, which was helpful when we were planning our trips around Paris (we did not take our own computers with us).
The location of the flat is perfect - close to a tube station, but also in a walking distance from the city centre (assuming that you don't mind 20-30 minute walks). There are many nice restaurants, bars, bakeries, etc. in the close proximity of the studio, and Canal St Martin's area would probably count as one of those where the Parisian alternative culture blooms and where the local hipsters like to hang out. Quite interesting.
Last but not least, I have to mention that we were really impressed by Cinderella's approach to beign a host. She had been very communicative and helpful throughout, and also very flexible around arranging for check in / check out times. But what made it special was the fact that she is just a really warm and caring person - we visited her at La Belle Hortense and she made our evening really great (not mentioning that she recommended great wines to us :)).
So do not hesitate to choose this place as your shelter in Paris and Cinderella as your host!