I stayed at Casa 400 for two nights in June on Business. The room was basic but more than adequate for my stay and comfortable with modern furnishings. It was spotless. I had no problems with WiFi reception in my room. Also, WiFi was included in my room rate (a bonus - colleagues at another large hotel chain had to pay extra)
Casa 400 is located close to Amstel Station and from there easy to travel across Amsterdam using the comprehensive tram system. When I stayed the metro system was being refitted between Centraal Station and Amstel Station, which made my transfer from Centraal to Amstel slightly more complicated than I had anticipated (I had flown into Schipol airport and caught the train to Centraal thinking I could then catch the metro ). However, there was a bus running between the two train stations (even at 9pm on a Sunday) so it wasn't a big problem. (As an alternative you should be able to catch a train from Schipol to Amsterdam RAI and then catch a tram - this may be easier but I haven't done this route, so check this first!)
I ate once at the hotel bar, the food was good and reasonably priced in my opinion. There was a little kiosk in reception that sold coffees/croissants in the morning - handy if you oversleep and so are in a rush (ahem).
My only caveat is there doesn't appear to be much in the way of other local amenities nearby the hotel (well I didn't find any) and it's located a bit out of the way relative to the city centre. But it's easy to catch a tram to go out if you want (gotta love the public transport in Amsterdam).
Overall, highly rated. I'd have no hesitation staying there again, especially given the price.