We love Sakamanga. This charming hotel's name means "blue cat" in Malagasy. The property is composed of numerous buildings tied together by winding hallways decorated with local art. The hotel doubles as a Malagasy museum with dozens of glass cases containing artwork, photographs, sculpture, skeletons, and tools spread throughout the grounds. In back there is a beautiful garden area where breakfast is served daily. The rooms are relatively small, but clean and pleasant. They have reasonable showers, which are hard to find outside of luxury hotels. The staff is friendly and helpful. All of them speak French and many speak English well.
Sakamanga has three spots to eat on the grounds including the garden area, a bar / restaurant serving french and local food, and a brick oven panini and pizza place. All are very popular and on weekends the bar is packed with locals and visitors. We enjoyed chatting with the bar tenders and sampling the local rum based drinks.
Several excellent restaurants are within walking distance of the hotel. We recommend Le Rossini, an upscale French restaurant and Arirang, an inexpensive Korean eatery.
Sakamanga also features an internet cafe and free WiFi internet connectivity. At 12-44 euro per night, this hotel is an absolute steal.
I know what you mean about central Tana, but Sakamanga was pretty quiet. Its on a small side street and the building is very deep (it goes into the center of the block.)