The location is very handy if you are arriving to Heathrow/Paddington. There is a walking distance to Hyde Park and Oxford Street. Several bus lines pass by. The underground is just a few blocks away. We liked a lot the charming Marylebone station close by. Mini Tesco was just a couple of blocks away.
The apartment is clean and cozy. We also enjoyed the views. The place is relatively small, however, even though there are three rooms. Is is okay is you are planning on just sleeping and relaxing during your stay. If you are planning on organizing dinners or spending much time inside, at least I found the dining+living room area relatively small and the kitchen quite simply equipped. The bathroom was nice and roomy.
I warmly recommend for small families or friends planning on seeing around London.