Great little place, close by to the train station and bus station / taxi rank. Only a short 5 minute walk without luggage, and maybe 10 minutes with it. There are some bridges you need to walk over with luggage and most don't have a ramp, only steps, so it can be a struggle. But still close enough to get to easily and you don't have to pay extra to get a water-taxi to somewhere else on the island.
From the unit, St Mark's square is only a 20 to 25 minute walk direct. But don't ever do anything direct. Wander the streets, explore the place, get lost, go into random shops, see the real Venice outside the tourist hot-spots which are crowded with people and Indians wanting to sell you crap. Local supermarket is 50m away.
The unit has enough to live with, considering you won't be in the place much. Kitchen is adequate, with pots and pans and cutlery if you want a chance to make your own home-cooked Italian dinner. It has a small washing machine, and we left detergent for the next guests. Air conditioners work perfectly.
It's a real Venetian apartment and gives you a small glimpse at how Venetians live themselves and I would recommend it.