Our stay was for two weeks and it was in the studio apartment, which served the two of us exceptionally well. We used it as a base while visiting London and doing overnight visits to other parts of England.
The room was clean, quiet, comfortable, and provided ample space. The area was nice and quiet. We never felt unsafe. There are a few stores nearby, which is important since you will need to supply your own food and bottled water. We found stopping by a M&S Food store while out in the city sufficient for our needs. There are a couple of restaurants nearby by but they are expensive and, TBH, not that great. You'll need to travel to King's St to find decent and affordable food.
Likewise, Chelsea is outside of the center of London, where most of the attractions are, but this is easily dealt with by using the nearby underground or the numerous minicabs that patrol the area. I recommend avoid using UBER. We had too many problems with them and resorted to just using the minicabs. Yes, it cost a little more, but you get drivers who really know the area. We were directed to some great restaurants and were given other valuable tips by drivers who grew up in the city. They often had stories to tell, which brought the history of the city to life.
In conclusion, this is a great location and my wife and I both agree that if we ever do another extended trip to London, this would be the place we would stay.