I stayed here at the Marriott Kensington for five nights a couple weeks ago, upgraded to a Renovated Junior Suite using my SNA certificates.
The lobby construction was still going on, and it was a bit of hassle but not unbearable. There was considerable noise at some times during the day, that I could clearly hear from my room on the second floor. However, things seemed to be quiet until about 10 in the morning, and no work was done on the weekends, so it wasn't much of a problem. The most inconvenient thing was that only one elevator was available, so sometimes there was a bit of a wait to get a lift up or down.
As best as I can tell, the Junior Suites don't all have the same layout, so don't expect your room to be exactly like the one on the website. But what I can says is, while there are a few layout quirks, I completely loved the room. The new design is great, with lots of style and character without trying too hard (a problem with too many recent Marriott renovations). Everything was very fresh and comfortable, and room had plenty of space -- including a round table with four chairs, a sofa, and *two* king size beds (inconceivable!). The bathroom had plenty of room too, with double sinks and a large counter. For one person the suite was almost too big, to where I could lose track of where I put things. I felt a bit guilty as I've know people living in London who've had a smaller flat than this room.
On the layout quirks (which may only affect some of the suites): 1) The sofa was perpendicular to the television and right up to it, so it really wasn't practical to watch shows from there. 2) The window was in a corner alcove, so you couldn't really see out unless you were in that corner. If you did look out, the view was through the glass canopy that drapes the front of the hotel -- and that gap between the window and the canopy had a lot of spider webs. A lot. My arachnophobic partner probably would have had to ask for another room. As for me, I closed the curtain which made the room perfectly dark and had some of the best sleep I've had all year.
I only got to the lounge a couple times during food hours, though what they had was pretty basic. Breakfast in particular seemed like the bare minimum, and on the instances I got down for that I found many tables were left covered with dirty dishes. It didn't bother me much on this trip, but those looking forward to lounge amenities would likely be disappointed.
The location of this hotel is a great compromise for vacation trip -- reasonably close to restaurants, tube stops and some museums while being a lot more affordable than staying in the City or the West End. Airport access isn't bad either -- a direct trip on the Underground from Earl's Court, and taxi / Uber trips aren't too bad either since you're already on the west side and can avoid much of the congestion.
It was really refreshing to be in a Marriott room so nice that I really didn't want to leave. Other than the lounge limitations, this truly was a great stay and I'm sure this property will be one of my first choices the next time I'm in London.
P.S. A protip for those staying here -- walking along the hotel driveway where it passes under the hotel is a good shortcut for heading towards the Earl's Court tube station.