Gianna's apartment is wonderful. Having stayed in a number of different apartments in Castello, I can confirm that Gianna's place was easily the best and is worth the price (it was a bit more than we usually pay but definitely worth it). It is in a fantastic location - the Arsenale vaparetto is a 4 minute walk, and it's perfectly located for the biennale or for San Marco and the tourist sites in Venice.
The place was very large - it had a separate kitchen, dining room, and living room - and was bright and modern. The shower was excellent (I don't know why but many places in Venice don't seem to have great showers), the beds were firm and comfortable, there was a washing machine (a blessing as we were there for 8 nights), a small outdoor terrace, great cooking facilities (which we used a lot), plenty or wardrobe space (but could maybe do with a couple more clothes hangers!), and best of all, it was incredibly quiet.
Gianna herself was wonderful - responding to messages straight away - and she even bought us a special local cake for Easter which was incredibly thoughtful.
I would highly recommend this apartment to anyone visiting Venice and hope to book it again when I return in future. Thanks Gianna!