As long as you know what you're getting, this is an excellent place to stay while visiting London. We were a family of 5 and were here for 5 nights.
The flat is setup as a series of rooms, each individually locked and with a strong door closer that actually makes it hard to keep the door open. There is no hang out space at all. Each room however (except for one) is large and comfortable. No A/C, but thats typical for London.
The good: Convenient to the tube, nice neighborhood, and there are nice touches (water bottles, welcome treats, a decent kitchen.)
When we came, the washer/dryer wasn't working and the company that was supposed to fix it didn't. This was a big deal since we needed laundry, but the housemaid (who is excellent, friendly and a lifesaver) was able to do it for us. The power also went out briefly (credits had to be added to the electric meter). Also one of the showers (the downstairs one) only had scalding hot water, so we only could use one shower.
Note: There are a series of flats that are rented out here, and when we were there it was obvious that some of them were being used by a younger crew that stayed up late. (which you could hear.) Not the landlords fault at all, but keep that in mind.
For our family, we'd probably look somewhere else that had some hang out space. But we made it work. The beds were comfortable and we used it as a base to explore London pretty easily.