I stayed in this flat for 10 days in June/July 2014. It is very cozy and comfortable, and has everything you need. Including a full kitchen, albeit small. The building has a lot of character. The lift is as old as the building and pretty small, and takes a while to get used to. The street noise can be a bit much, but the flat is on the 5th floor (4th floor by European standards). I didn't mind any of these characteristics because I love a true cultural experience.
I was able to walk everywhere, except to long distance places. The best restaurants, coffee shops, clubs, bars and theatre shows are all within 10 minutes. There are several tube stations nearby, and Kings Cross is about 15-25 minute walk.
If traveling alone, or with two people, I would HIGHLY recommend this place. It's not a huge property and the bathroom is a bit tight, but that is typical for London and other urban places.
Once again, I would definitely stay here on my next trip.