We really enjoyed our stay at Villa Sonja. It was very reasonably priced for a clean room that had everything we needed. We especially appreciated the free airport transportation. We also appreciated that when we checked-in we were given a map of the area and told about things in the local area and how to get around.
We stayed in the studio for 2 people. We had a kitchenette (fridge, 2 hobs, microwave, sink, coffee machine), table and chairs, TV, wardrobe, bedside cabinets, bed and bathroom. We found the bed a little uncomfortable, but this was not a major problem. We were surprised there was no blanket on the bed (just sheets and a slightly padded cover), however we didn't need one, although one night we were slightly chilly. Had we really needed it, I am confident that we could have asked the management, who seemed friendly and helpful.
Villa Sonja may not be in the centre of Zadar, but you can get there either by bus or by a 35 to 40 minute walk, or 50 minutes if you take the route along the coast (walking about 3mph). With the coast and beach nearby, we found it well placed to investigate the area. There was a nearby supermarket and bank.
Our stay was very positive, and the negative things I've mentioned were only minor, especially given price. The only other thing was that we could only pay by cash (which retrospectively isn't surprising considered it is a small place), but having booked through Expedia with a credit card, it took us by surprise on the last day.