We stayed for 2 night at the Nadia in Mid January. Staff were lovely. The pictures of the stairs you will see on the internet do not do justice to how steep they are, typical I suspect of many hotels. Our room was small and serviceable. Yes the window is draughty, but you don't realise until you draw back the curtains. We were never cold. My Husband was awoken by the church bells (every 15min/hour hour?) and when the trams are running it can be a tad noisy - however after all the walking I was out like a light so dint bother me :)
Location is perfect. Just behind Dam square and 5 or 10 min stroll from the Station.
The only reason I wouldn't return to this particular hotel was the fact that the bed was up against the wall and I like a bed where you can get in and out from either side.
Apart from that great price, good facilities, great location especially if you make Anne Frank Museum your first port of call as it is so, so near :)