Ellen's apartment is what american real estate agents would call a "bijoux." Small, but really well thought out. Even utilitarian items like a toilet roll holder have been chosen with care. The first thing i noticed when i walked in was the welcome gift on the breakfast bar. A great way to start your stay.
The apartment overlooks the gardens in the back. You won't hear any traffic noise from the street in front. As i mentioned before the apartment is small but easy access to a decently sized terrace increases the amount of space you have. It comes with a sturdy table and two comfortable chairs so eating outside is a comfortable experience. Since the space is right underneath the roof and it CAN get hot in the netherlands (although not very often) Ellen thoughtfully supplied the apartment with a state of the art A/C (= not noisy) to cool down the space after a hot day (it was 28 degrees C/82 F when i walked in.)
The hostess stocked the place with all the necessary items (shampoo, shower gel, coffee, tea, oil/vinegar, dishwasher tablets, etc.) so you don't have to start your stay with a round of shopping for essentials.
In case you're wondering about the location (central enough?...) The number of tourists in Amsterdam seems to have increased dramatically in the last 10? years or so. As a result, IMHO, the downtown area and anything near it needs to be avoided at all costs. It has become a total tourist trap with so so food at premium prices. One way to get around it is to stay in less traveled areas, like Oud Zuid (where the apartment is located.) You still have easy access to the heart of town but there are way more interesting areas to explore: Amsterdam Zuid, Oud Zuid, de Pijp and so forth. The nearest tram/lightrail is only one block away and can take you anywhere you'd like (although you may have to change trams somewhere.)
One last note: if due to health issues you have trouble walking up the stairs, this apartment is not for you. It takes 4 Amsterdam style (= steep) stairs to reach the top floor.