So first the good. The apartment was clean and just as described in the listing. It's modern and comfortable. I did not meet the hosts but they left me detailed instructions for getting into the flat and I had no problems.
The flat is on the 2nd floor and the staircase is quite narrow. There is no lift in the building (or that I saw anyways).
I had no troubles with the flat and everything was as expected, but a couple of things were odd. There are quite a lot of rules for this flat. And by quite a lot I mean you get a huge illustrated instruction manual with dozens or hundreds of conditions. It's intimidating and one seriously wonders how many hours got put into creating this epic tome. Answered in part because one of the rules is a three digit fine for misplacing or abusing the manual itself. I had to pay extra for a 2nd set of linens for my companion, but, again, they clearly spelled this out in the listing. I get the feeling that having any problems with the flat, like missing or broken items, could go really badly very quickly. Some rules seem out of a psych experiment, like, you must not get water in the bathroom, but, the shower stall door does not seal closed and it's a waterfall shower, so this is basically impossible. You have to put towels everywhere. Feeling like I was in a graduate research project was a bit off-putting, so I do not think I would stay here again.
The location is wonderful if you are not familiar with the Hammersmith area. This is currently my favorite place to stay when visiting London. Everything is walkable and you are right on two underground lines.