My wife and I stayed here for a week in August 2006. The house was cosy, clean and well-appointed; we found it exactly as it appears in the photos. Jason (the owner) was very friendly, helpful and laid back. Having briefly shown us around the apartment, he handed us the keys and told us to let him know if we needed anything.
The apartment is an absolute bargain! It is so close to the city that you can walk to Rundle Mall, yet its location in a little one-way street means that it doesn't get any traffic. If you don't feel like cooking, that's fine; the Hutt St cafe strip is just around the corner.
Alternatively, you can walk round to the front of the building and have a great sit-down meal in Jason's cafe. We found his hospitality charming, his food excellent, and his prices very reasonable. I can definitely recommend Castle Apartment to anyone spending time in Adelaide. :)