Marusca's apartment is absolutely lovely. Truly fantastic location that is right on the Arno river and overlooks the river. The location is perfect as well; a short walk to get to the historic center and has quite a bit of very good restaurants within a 5-10 walk...and if you love gelato, it's only only a couple of blocks from Santa Trinita and La Carraia.
Check-in was super easy by communicating with Marusca; she's very responsive, accommodating, and gave us some great tips on where to eat in the neighborhood. The apartment is located on the top (3rd) floor and there isn't an elevator. We had no issues with walking up the stairs. We had a rental car and there is gated private parking behind the building. The huge bonus: the apartment is not in a ZTL (it's right on the edge of the ZTL) so you'll be able to drive to/from the apartment without issue.
Highly recommend and would stay again next time we're in Firenze!