Since La Maison Favart is #1 hotel in paris on tripadvisor at the moment, I can't say anything better than all the reviews below. but still adding some personal impressions..
This is such a beautiful boutique hotel. I strongly recommend to stay if this is in your budget.

Lobby was fabulously decorated with class.
Room was beautiful and exquisite. I loved that they kept the original ceiling wool construction and just painted to match the interior. I was totally in love with the art deco shaped huge crescent/arch window wide open to the little square in front of the hotel.
Nespresso machine in the room is definitely a big plus.

Most of all, I have to say the service is better than any super fancy hotels I have stayed all over the world. The concierge was so professional, knowledgeable, nice and even with sense of humor! You really do feel like you are treated so special!

If I have to say one little thing, it's really hard to park around. so as anywhere in the center of Paris.

Over all it's super excellent. and you won't regret to choose this hotel!
Enjoy!

Only small complaints were the small size of the deluxe room (26) and the wrong (double priced) buffet breakfast on our bill instead of the continental breakfast. That out of the way; the hotel's location was perfect for access to the famous monuments, we easily managed to walk from the Eifel Tower to Notre Dame to Sacre Coeur then back. The hotel is tucked away on a small quiet road next to the Opera Comique, less than one minute from the Metro Richelieu Drouot. The period building is stylishly and comfortably decorated and impressed when we walked in. The staff offered us a warm welcome and were really helpful throughout the stay. Hakim, the concierge was especially helpful, giving us excellent restaurant recommendations based on what we described we wanted, he even printed of Google maps so that we could easily find the restaurants.
The bar area and lounge were relaxed with log fires that helped warm us up after walking around in -1 degree temperatures in the day. The sauna and well-being area were also perfect for recouping from hours of seeing the sites. The room was spotless, with a world class bed and pillows and a modern style bathroom with bath tub and shower – so all good.
Will definitely pay another visit.

I had a quite a few misgivings about staying here, given the stress and hassle of trying to book with the hotel directly 2 x interconnecting/adjacent rooms for my family. Lots of confusing and contradicting emails from the hotel. The hotel itself is a small boutique, the rooms are comfortable, facilities are limited and is in a good location, 10 minutes walk from the Louvre. The hotel concierge gave us 2 x really poor restaurant bookings, despite having given him a pretty detailed brief. Maybe it was my accent. I can see why Maison Favart is well-regarded and popular, though on this occasion, it just didnt really work for us. I will add, though that by Paris standards, its very good value.

A boutique hotel situated in a quite location in Paris. Close to the metro, fairly central. Small reception area, front desk manager was helpful and polite. We booked a classic room. The room was very small indeed, it had no drawers and only one narrow cupboard which also contained the safe and a mini bar. There was no room to put 95% of our luggage (we had only 2 small suite cases). We booked the hotel mainly because of its pool. We found that it was closed for the entire time of our stay for cleaning.
After speaking to the front desk manager and advising of our dissatisfaction, we were upgraded to a suite. I highly recommended to book a suite as its an utterly different experience. Its like a small apartment. It has a lounge, 2 bathroom and a bedroom. The suite was very quite. Hakim the concierge was brilliant, he is very good in advising various locations to visit etc. and keen to assist. Breakfast was delicious and had various dishes and lovely coffee.
The rooms and the hotel in general is very clean. Highly recommended.