Great place to stay while in London -- my flat was absolutely immaculate and the building was very nice and well-lit. The room itself was small, but a perfectly acceptable place to lie your head down at night after a full day of exploring. The bathroom was a great size, though. Be prepared if you have a bunch of luggage, or just very heavy bags -- there is no elevator. Overall, this spot was perfect for a solo traveler. If you arrive before check-in, you can leave your luggage in the host's office to get started on seeing the city.
One thing to note is that there's no mini-fridge. I know there's no kitchen, but for some reason I assumed there'd at least be a mini-fridge, which was totally on me. However, be prepared in case you have food/treats you need to store.
The apartment itself is in an excellent location -- I cannot stress this enough. It's close to a few Tube stations + bus lines, as well as major sights -- Kensington Palace + gardens and Hyde Park. It's also just a few blocks away from Dishoom Kensington, which is an absolute must-try if you're here.
I would 100% stay here again!