Great place. I wouldn't hesitate to stay here again. My wife and I and our two sons (14 and 10) stayed here for a week. The boys slept in the loft and it was perfect for them. The place easily has enough room to accommodate four people.
The location is a quiet street next to the Sorbonne. There is a small courtyard with a fountain and a couple restaurants. It is quiet (except when France wins in soccer). You are close to the subway and just far enough away from the more crowded sections near the Seine. It is an easy walk (less than 30 minutes) to most places; 10 minutes to Notre Dame for example. There is a grocery store a block away. There are ample restaurants that are less touristy nearby in the Latin Quarter.
Kelly was a great host. She contacted us regularly to see if we needed anything. She monitored our flight into Paris so that someone would be at the apartment to greet us when we arrived.
Don't think twice about booking with her.