If there's a message to call about redeeming for free nights, it usually means all the regular rooms are sold out. You might be quoted a higher redemption rate for an "upgraded" room.

The LM also comes up often on Travelzoo for pretty good rates.

As for location, it's not bad. Close to the metro, close to local restos, and a mall (with supermarket) is across the street. If you're arriving at CDG, the Air France bus stops right in front of the hotel.