I booked 2 rooms in the Relais Christine - one for my inlaws and one for my partner and me. For reasons I won't go into, one room was booked via Booking.com with a pay in full in advance rate and the other was booked through Small Luxury Hotel's The Club (affinity program). The booked through SLH was upgraded, included a wine amenity and breakfast daily... in courtyard room #1. The Booking.com reservation was in room #19 and did not include breakfast, wine or an upgrade. There was a very small difference in price so, lesson learned: Joining The Club and booking via slh.com is the best value by far!
The rooms themselves were quite nice and small, as is to be expected in Paris. But one should be out exploring the town anyway, and this location is SO CLOSE to museums, great restaurants, etc. and we took advantage of it. We really enjoyed the honor bar in the lobby as it seems many other guests have as well. Our rooms were very quiet - we didn't encounter some of the noise issues others have mentioned - but perhaps it's due to the time of year since it's not tourist season. A good AC/heating system, two sets of blackout curtains, and a pocket door between the bedroom and door to the hallway made for a great sleeping environment.
The staff is excellent and had stellar recommendations for dinner. We especially enjoyed Pinxo and La Rotisserie d'en Face, both less than 5 minutes away by foot from the hotel.
We couldn't find fault with the hotel and recommend it. The price is high but the value is as well! If you visit in December, be sure to visit one of the local Christmas markets and check out the animated storefront windows at Printemps and Gallerie Lafeyette.