The flat is very well located - the Cafe Noir bar downstairs has very affordable drinks (which we actually found to be the case throughout Venice much to our surprise), and you can walk EVERYWHERE.
I've stayed in plenty of airbnbs, and generally I think they're good value for money. Personally I think this particular flat is overpriced, especially when you add in any checkin fees due (it's only free between 1pm - 7pm), cleaning fees, and tourist tax - all of which must be paid in cash on arrival. All of these are detailed on the booking but still feel a bit odd - it's not something I'd encountered on any airbnb bookings in the past and made a £300 booking almost £400 when I paid the cash on arrival.
The flat itself is perfectly adequate although we couldn't find pillow cases for the spare pillows, or the hairdryer, and there wasn't any shower gel or shampoo provided (not essential but a nice touch when you're coming for a weekend with airport liquid restrictions - and paying a decent chunk of money). We also couldn't make any of the blinds work - the pull cords seemed to be broken (or disabled maybe) on all of them. On a January day you do want to let the light in as much as possible...
Venice itself is BEAUTIFUL and we had a fantastic weekend, the flat just fell a bit short to be honest.