We spent four comfortable nights at this place last month, right across the square from the station and therefore 20 minutes from central Amsterdam. It's about ten minutes down the street to the Grote Markt. We had inquired about an elevator since my wife has trouble with stairs, and they had replied that they had one. When we arrived they put is in a ground-floor room a few steps from the lobby. It was good-sized by European standards, with good facilities and comfortable twin beds. Besides heavy light-blocking curtains, it had lighter curtains that allowed us to see out to the street (not especially attractive) but blocked views of the room from outside (we checked).
The three desk clerks we met were friendly and very helpful. A transport strike was planned for one of the days we had to get to Amsterdam, and we had trouble figuring out its scope, but the desk guy worked through it with us until we were sure it wouldn't affect the train. He also pointed me toward a convenient laundromat a couple of blocks away.
The hotel has a friendly uncrowded bar and restaurant, apparently serving mostly guests, and perhaps the best breakfast buffet (included in our rate) we've had in a European hotel. Best croissants I've had outside of France. There's a guest computer in the lobby and wifi which worked better in the lobby than in our room.
I'd highly recommend this place for visiting Haarlem or for a low-key alternative when visiting Amsterdam.