Sophie's place is a great choice for its value. It's not too big, but during our stay in Paris, we walked around the city most of the time, so we just needed the place to sleep (and the bed is super comfortable). Also, the location is great and the St Martin channel is beautiful.
The only bad thing was that the apartment was in the 5th floor of a building without elevator and we were carrying three big suitcases with us. But if you have strong legs or less luggage, this is a perfect place for you.