We stayed in this apartment for three days in January 2011. It is walking distance to everything. It is on the other side of the river from the castle and the main old town, but Salzburg is small enough that everything is walkable.
The furniture and design is quite new, with a good layout, so that it feels reasonably roomy for its 80 square metres.
The only issue is the kitchen. There is no conventional or microwave oven, and not all that much equipment if you would like to cook even just on a stovetop. We managed to make pasta, but much more than that would not be possible. In fact the pizza we bought is still languishing in the freezer of the apartment!
The agent was very helpful, and met us at the apartment and showed us around. There is a supermarket very close, although it doesn’t have a great selection, and the Wednesday market is just around the corner.