We stayed at the apartment for a whole week and enjoyed our stay very much. The apartment is cozy, spacious, quiet, well-equipped and just very very pleasant (looks just like the pictures).
The building itself is very nice, and so is the neighbourhood. It is in a quiet area, and takes about 15-20 minutes of walking to get to the center (or 8 minutes to the nearest subway), which was ok for us.
The reason we did not rate it full 5 stars is due to issues with the internet not working well (which I understand should be fixed soon - they were working to install a new system), and the bed was rather narrow for two people (I think it was less than 1.40m-wide).
Taking all into account, this is a very nice stay in London.