Paolo was an excellent host, who has an awesome apartment. It was large, with plenty of places to sleep, very clean, had everything we needed. It's perfectly located to walk anywhere in Venice. Paolo told us about places to see, areas to eat at, and responded to questions we had promptly.
He was very flexible in terms of checking in and out. As one of us had a later flight on our checkout day, so Paolo very graciously agreed to let us leave our luggage at the apartment until it was time to head to the airport!
The one concern about the apartment, like many others have mentioned, are the stairs going up to the apartment. If you have difficulties going up stairs, they may be a problem. But for us, they weren't a major issue.
We would recommend Casa Sofia to anyone who wants to have a comfortable stay in Venice and would definitely stay at it again next time we're in Venice!