Great Location (Tube 10 minute walk, restaurants, bars, and shopping a few within walking distance in all directions). Larger than expected (based on pictures). The rooftop is the "awe" feature that convinces you that you made the right choice from the hundreds of properties in the surrounding area.
The twin beds in the smaller bedroom were more then adequate for our daughters (Ages 16 and 20). Response of host prior to and during the trip was instantaneous.
The only basis for hesitation should be the 4 flights of stairs should you have an elderly/limited mobility member of your party. Of course, the benefit of the 4th floor flat is privacy from the street, nice breezes throughout the day, and the previously mentioned roof terrace.