My husband and I really loved our stay here. I almost didn't book it because of some negative reviews, so I'll comment on those, to help anyone who's unsure!
Stairs. Yes, there are lots, and they are steep. That's because you have an amazing flat at the top of a traditional Amsterdam house, with a roof terrace with great views. You do need to hold on with both hands to the banisters on both sides.
Check-in. We were met by the host's friend, which we had expected, and that was fine.
Security. There is no lock on the front door to the apartment. It's up two flights of stairs from the host's apartment, though, so it feels private. If you are security-conscious, it might worry you; but I mean, the host *always* has access to your Airbnb, whether it's locked or not, right?
Mice. We did not hear or see any trace of them; the place was extremely clean. The plumbing does make unusual noises; perhaps that's what other guests have heard.
Sagging beds. Both beds are, I think, two single bases with a double mattress on top. This didn't bother us, but it might do some people.
Overall we found the place charming and comfortable, in a quiet location that's nevertheless close to the Jordaan, the museums, and the Nine Streets shopping area. We would certainly stay here again.