My wife and I stayed for two nights at Ada's studio. It was clean, cozy, tastefully decorated, excellently located; just around the corner of Piazza del Duomo and Piazza della Repubblica.
Even though we didn't have the pleasure to meet Ada in person, the communication before and during our stay was outstanding; she quickly responded to our messages/questions.
Both a welcome bottle of wine and a notebook with her hand-written recommendations were a nice personal touch, which we enjoyed very much.
In the end, we regretted not having spent more time in Firenze (and at Ada's place). We'll certainly be back at some future time and stay at Ada's.