This is a great place to start exploring Amsterdam from: close to every cool place in the city and in walking distance to most sights. There are a lot of locations around for food and food shopping, bars and restaurants. You can rent a bike right near this place, and you also get some shower/cosmetics supplies at Etos and have your coat dry cleaned if needed - all in the same little area! If you spend here 1-2 nights, this is a great place!
I spent a month in this place as I was relocating from USA - and I would say that for long stay, this is not a suitable place. The amenities are far too few, no cooking possibilities and you have just a few hangers on a door (not a clothes rack, no wardrobe or a dresser for clothes).
The good part is that Frank is really open to feedback: the towels he gave me initially smelled musty, cheesy - due to the humidity - Amsterdam is wet! I have extremely sensitive skin (Lupus) and I was afraid of using them and Frank was kind enough to bring me a ton of fresh ones!
Frank also gave me a lot of freedom: in the 4 weeks I was there, we barely intersected and offered to clean my room and replace textiles regularly.