My wife and I stayed at the Citadines Batille Marais in March 2008. We were very happy with the entire experience. We stayed in a 1 bedroom apartment for 1 week. The location was great with 3 different metro lines within a few blocks walking distance. There is a food market across the hotel on Sunday and Thursday which is a great way to stock up on fresh fruits and cheeses for breakfast every morning. The kitchenette was a perfect size (we only had breakfast in the room). There was internet connection which allowed us to stay connected. Also, the size of the rooms were great for European standards.
5 min walk from Breguet-Sabin metro station, great location.
Small but well-appointed apartment - but had some problems getting twin studio as booked, and then had an extremely dodgy fold-out bed. Also overpriced laundry and cleaning only once every seven days.
Seems to have deteriorated a bit in recent years - stayed twice before, in 2001 and 2006, when it was much better.