First, location: Amazing. A few steps from the bridge into old town (restaurants, museums, etc). Backs on to a walking street (shops). We walked from the train station to the apartment with two small children, luggage, and a stroller in about 10 minutes.
Second, the apartment: Outstanding. The hosts have obviously put a lot of thought into everything. The flat is completely wheelchair accessible (if that's important to you). There is a clothes washer/dryer (yes, a dryer!), dishwasher, fridge, and microwave/convection oven. The beds were very comfortable and the heating works perfectly (radiant heat in the floor). The shower is wonderful--plenty of pressure and controls that work as expected.
Overall: Excellent. Highest recommendation.