I have travelled to, and stayed in Amsterdam many times. Without question, the NH City Centre is by far the best place I've stayed.
Now, lets just put this in perspective, yes, the rooms are a little small and perhaps compared to other cities, a bit pricey, but you have to compare this hotel, not to all hotels in the world but to other accommodation in Amsterdam - and it is by far and away the best deal you can get for your euro - for Amsterdam City centre, it is great value.
The location is perfect - just off Spuis - which puts you on the main tram lines and within minutes walk of Jordaan, the best area of Amsterdam and within minutes walk of all the tourist attractions in Amsterdam.
The decor is modern, and clean, simple, all you need for a weekend break. with a few nice touches that remind you, you are in a friendly place. I found our room to be spotless.
Finally, the staff are Brilliant. Everyone from cleaning staff to reception and above had a warm smile and were always attentive and happy to help. I cannot rate their service highly enough. Considering the amount of tourist traffic this hotel gets, I can tell you this is no mean feat.
In my opinion the reviews here that give this hotel less than 4 stars do not understand the accommodation market in Amsterdam or are expecting way too much for their euro.
in short, perfect price, perfect location, perfect staff.
[ by the way, if you do travel to Amsterdam, do yourself a huge favour - don't bother with the red light area, it's horrible. Hang around the Jordaan and go to the great art galleries and café's and eetcafés. You will go home relaxed and feeling brilliant, instead of frazzled, ripped off and vaguely disappointed in humanity ]