Such a great location - we really loved being in the Rialto Market/Rialto Bridge area. You really couldn't pick a better spot as far as I'm concerned.
We are 3 adults and I would not consider this a suitable location for 3 adults, myself. There was 1 bedroom with a double bed and a small den with a pull-out love seat. The love seat did not have a bed mattress, just the couch cushions. I think this would probably be fine for a child but for an adult, this took up the whole room without room to move around the bed. My suitcase had to go in the kitchen area which was already very tiny and made it so that our only place to sit (the kitchen table) was unable to use. We weren't there to stay in the apartment - we were there for Venice! But it did make it a bit difficult to function in such a small space.
The toilet is up on a step which may sound funny to comment on but it actually made it very, very difficult for my shorter friend to use.
If you want more than one very flat pillow, you may want to plan to bring something along with you and if you want to use the washing machine - you probably need to learn to read some Italian as there weren't English directions.
That being said, it was clean and a great location. For 2 adults, I think this would be perfect.