Me and my boyfriend were in Florence last weekend for the half-marathon. We stayed at Aviv's house and we were happy to find out that the house is actually more spacious than what it looks like in the photos. It's a nice little flat, very cozy and also very clean. We only stayed one night and we were out most of the day, so we didn't have a chance to try the kitchen, but everything else worked just fine and the bed was very comfortable.
The checkin was perfect and communication was very easy. They were also so kind as to let us checkout later in the afternoon as we requested.
The 5 floors of stairs didn't really bother us much (it's like a mini workout every day), although I guess they were a bit of a pain after running the half-marathon!