Spent three nights here and loved it. Well-appointed room, comfortable bed and soft bedding. Lots of light and very airy with cheerful decor. Great location.
The B&B is in a typical Amsterdam rowhouse, meaning lots of steep stairs (although this is true for all Dutch houses, especially in Amsterdam); this shouldn't be a problem, just double check that you have everything before you leave for the day! The rooms are average size, the bathroom is small but very well-designed (the whole room turns into a shower, which is very cool).
As for breakfast, we were provided with many kinds of bread, cheese, cold cuts, and fruit as well as butter, jams, nutella, cereal, milk, and juice. All we had to do was pop some bread in the toaster and make coffee in a very easy-to-use machine (using coffee pods). For the sake of comparison, I stayed at an actual hotel (as opposed to B&B) in Leiden, with a real dining room and full breakfast service. That service consisted of two slices of toast, a variety of untoasted bread, a plate with three slices of ham and three slices of cheese, and an assortment of spreads (jam, butter, nutella, sprinkles, etc...). There too, I had to get up to pour my own juice or make myself a coffee using the automatic espresso machine. It is nice to eat in your room, you can even have breakfast in bed. And it's not like they expect you to wash the plates!
In any case, Amsterdam is a lovely city (best seen by bike, which can be rented at numerous locations) and this is a great place to stay when visiting.