Our group had a great stay in Paris largely due to our superb accommodations in this apartment. First, the location is absolutely ideal at the corner of Boulevard Saint-Germain and Boulevard Saint-Michel. Your just steps from a metro station and short walks to the Seine, the Louvre and the Luxembourg Gardens.
Next, the apartment was such a contrast from a hotel with a nice kitchen, very spacious living room and two baths.... Not to mention an incredible view of the boulevard below and glimpses of the Eeiffel Tower in the distance.
Finally, the owner was quite accommodating in terms of arrival and departure as well as checking in during our stay (by phone) to make sure we were well taken care of.
Couple of notes: we were worried the location might prove noisy; it wasn't at all with quality windows. However, it was cool while there and if you needed to sleep with windows it might be an issue. We never inquired about air conditioning as we didn't require it.
The apartment is on a high floor but has a small elevator which was quite helpful when luggage was transferred.
Overall, great place and really a bargain when compared to a hotel for multiple guests.