We stayed in Carmela's listing for three nights, and found it a really lovely experience. There were some problems with our train from Rome, which meant that we arrived into Syracuse 2 hours behind schedule. Carmela's husband was kind enough to pick us up from the station and drive us to the house!
The house was a really good size, with a downstairs kitchen and living area, and two double bedrooms and a bathroom upstairs. There were only two of us, so we were able to have a bed each, and had plenty of room to call our own. The kitchen was well stocked with plates, cutlery, cooking equipment etc and the air conditioning worked really well, which was great for August!
In terms of location, I probably feel that staying on the mainland is better than on Ortygia, since it is much quieter and less touristy. Also, the house is equal distance between the Greek ruins and Ortygia, so it was a great base for the island! I would definitely recommend Carmela's house and hospitality!