Me and 2 friends had the pleasure to stay at Christian's apartment for 4 nights. The flat is very spacious. The bed is perfect for a couple, and sleeping on the sofa is comfortable as well (provided you're not too tall). There's no window blinds, but if you don't mind sunlight waking you up that's fine. The pictures give quite a good impression of the flat.
Christian was very flexible and uncomplicated, and made sure we had all the information we needed for our stay. The flat is located a few stops by metro from the centre. Walking from the center takes about 20 min, but there's metros running pretty much all the time.
I can recommend staying with Christian.