My stay at the B&B Ancient Venice was pretty good, but had several technical issues.
The location is convenient, about 10 minutes walk from the train and bus station, and just 100 yards from the Ca' Rezzonico boat-bus stop. It's easier to find coming in from the airport on the Orange line, stopping at Ca Rezzonico. Once you are settled, you can follow the signs to the train station (Ferrovia) for day trips.
The room was big enough for two, and you can access the breakfast room at other times of the day for an espresso or a snack.
The issues I had were with the wifi and the TV. The wifi was spotty, and would shut off suddenly, saying I had reached the maximum, even if I had been out all day. It resets after midnight, but can be a problem, as when I was trying to connect with friends, and needed to use email. Also, the TV never worked in 6 days. Paolo, the owner, who is not on site, said it was an antenna problem, but it didn't seem like it was being fixed.
The bathroom is not private, as advertised, and could be a problem when there were others using it. Also, there is no A/C, (understandable in an older building). There is a fan to use which helps, but you want to keep he windows closed at night, since mosquitoes come in.
So, this is a good spot, but have a back-up plan for using the Internet if you need it.