UPDATE (long overdue).
I spent three nights in early June at Hotel Lion d'Or and enjoyed it. The weather was a bit blustery that week, so I cannot comment on comfort on hot and humid days. (Note that I found Amsterdam overwhelming and expensive, and preferred returning to smaller Haarlem in the evenings. The train to AMS Centraal was easy. I also much preferred Utrecht and Delft to Amsterdam.).
The hotel is a wee bit tired, but very well maintained and cleaned. My room was on the third level at the rear, overlooking a side street, so I had no noise. The room double-bed was small even for a solo -- not enough room to swing a cat, but I travel carry-on and did not bring a cat so that was not an issue. I did have sidle around the end of the bed to get to the desk, but again, a non-issue. The usual amenities of coffee/tea maker, WiFi, etc.
The common area/bar/restaurant opens to the train square and is pleasant; you can sit there without being pressured to buy food/drink. I am not a nightlife person, so being away from the central area (7 minute walk) was fine with me -- a quite drink on the hotel square was lovely in the evening.
CONCLUSION: I would definitely return to the Hotel Lion d'Or if I were to be in the Amsterdam area again. I'm a serious "mid-budget: is it clean and safe and well-located" traveler, and it fit the bill.
NOTES:
I found Amsterdam overwhelming and expensive, and preferred returning to smaller Haarlem in the evenings. The train to AMS Centraal was easy. I also much preferred Utrecht and Delft to Amsterdam.
If you want to visit the Corrie ten Boom house, make reservations the moment you know your Haarlem dates ... and it still might be too late
The GrosKirk is fabulous. The tours are led by parishoners who love their church; the wooden ceiling is amazing. The organ is one of the best in the Netherlands; look at the church notice board or online for concerts.