I stayed at this hotel twice. Its location is perfect, close to RER Station Luxembourg (trains to Airports Charles de Gaulle and Orly), Luxembourg Garden, Sorbonne, Pantheon and Middle Age Museum (Cluny), all within 5 min on foot. Within 10 min: River Seine, Ile de la Cite, Notre Dame Cathedral and the famous cafes of St Germain des Pres.
The hotel was renovated a few years ago. The rooms are comfortable, clean and very quiet.
The breakfast (not included) is poor (only tea/coffee, bread, butter and jam), but there are a lot of restaurants and cafes nearby where you can have it cheaper and better.
I would recommend it.