Having stayed in Siracusa before, within Ortigia, we were plesantly surprised by how much space there was - with three good size bedrooms, one with a walk in wardrobe, two bathrooms, two living rooms, a kitchen, a terrace and even a utility room to do your washing. The building itself is fairly quiet, and you're on the top floor. I was pleased (and surprised) to see that there's a good size safe fitted inside a cupboard - big enough to store passports, cameras, laptops, the lot.
Beds were comfortable, and it wasn't too noisy outside at night, the kitchen facilities were great (it's nice to have a proper oven, in previous Sicilian Air bnb's I've stayed it seems hobs + a small toaster sized oven are the norm, but here you're treated to excellent kitchen facilities). The terrace is great and certainly catches the sun most of the day. There is wifi but I'd recommend using telephone data anyway as it's a bit quicker.
The location is pretty good too - it's about 15 minute walk to the edge of Ortigia and about 15 minutes to the Greek Theatre (and other historical monuments) so, while you may not be in the most lively area, you're well situated to get everywhere. You're seconds from one of the main roads anyway, so it feels a safe walk. Parking is available on the street, once you've navigated the one way system. All in all having stayed both on and off Ortigia I'd recommend Stefania's place - you get a much bigger apartment for your money, with more facilities and (although we didn't need it in January), proper air conditioning across the whole flat.