For my first trip to Paris, I was looking for something pleasant and budget-friendly. L'Hotel de la Paix exceeded my expectations. It was recommended by a friend who travels to Paris frequently, and I was very happy.
The location is excellent -- a half-block from the Metro and a five-minute walk from the RER to the airport. There were many, many good restaurants nearby, and the Luxembourg Gardens were a short walk away.
The staff was pleasant and helpful, and the rooms were very clean. I was particularly impressed by the newly remodeled bathrooms.
I stayed for five nights in a superior double room and three nights in a standard double. The superior room was quite spacious (for a city hotel, that is.) The standard was a little tight, but it was still very comfortable.
One caution -- although there is a small elevator, you will still have to carry your bags up or down a flight of stairs. Also, if you're a light sleeper, choose the superior room where you will hear less hallway noise.
Just a very nice, comfortable, not horrifically expensive place to stay if you want to explore Paris. Highly recommended.