The double bed, singles lashed together like an emergency raft, was tremendously uncomfortable. Only by folding a great deal of bedding over and doubling up could you no longer feel the jab of springs.
The room was certainly clean. The room's condition was ok in general, though the wardrobe doors slid open if you tried to close them and the shower was missing one of its sliding doors.
Yes, it's located very close to Piazza San Marco, but there's no reason to be drawn in to paying for location alone. Venice is small - I walked back to the Alilaguna terminal at Fondamente Nove in about 20 mins - so you needn't be afraid of staying further out.
When checking in/out, you need to do so at the Hotel della'Opera about 5 mins walk away, which wasn't made too clear on this site when booking. The staff there are pleasant and will give you a map should you need one.
WiFi was fine, the building is down a little side street near to a few restaurants and shops.
I wouldn't stay here again. I expected a level of comfort that was missing. Try elsewhere, or save money to spend enjoying Venice, which is a wonderful city.