We had a nice stay here. We had two couples staying at the apartment. It is well-located and is about a 10-15 minute walk from King's Cross/St. Pancras, so you can get just about anywhere of note in the city within a 30 min. There are also a number of decent restaurants nearby. The apartment was clean and the front room had enough room to relax. Overall, it would be a pretty good value for 2 couples or families with 1-2 children (someone could likely sleep on the expandable couch as well).
The main downside of this place is that it's located right above the railway so you can hear/feel the trains passing when you try to sleep. Also, the neighbors were quite loud. Just remember to bring earplugs!