Short version: All in all, would 100% recommend to 1-2 travelers; SUPER conveniently located to a train station that often gets a stop on the limited Keikyu Line; incredibly thorough host in terms of information. Supremely clean and stylish!
This is probably one of the most convenient locations you can get if you're coming from Haneda airport, so if a super quiet, bright, stylish home base is required, this is an excellent choice. It's only 5 minutes from the airport, and if you catch the limited trains out to Shinagawa, you can be on the Yamanote line in about 10 minutes or so. This is great if you have friends you want to visit in Tokyo, because then you just ask them to meet you at Shinagawa station! However, if you want to visit Shibuya and the like, it does take a little longer (but not much longer); those parts of town were not on our list.
However, Tokyo Disney Sea WAS on the list, and we had incredibly good luck with getting onto trains that weren't crowded. Because this is Tokyo, make sure that you do some research about when rush hour can be expected; and because this is a location convenient to a station with limited express trains, have a look at those (but make sure it actually stops at this station). There were probably more direct ways to get to Disney, but our train adventures were totally fine. And also...seriously, do research on what to expect, because it's quite normal to be on a pretty crowded train, and it helps to know what to do.
In terms of the space, it was incredibly bright, squeaky-clean, and funky with all the art pieces around the area. If you are a tall person (in our group was one person who was a little over 6'0"), you may accidentally hit your head on the low-hanging lamp, so just be aware of that. I think this is best for a solo adventurer or a couple of people traveling together if you are not used to smaller spaces. Remember, this is Tokyo! We had four people in our group and it took a little bit to figure out how we could exist in the space together, and I think that would be the maximum, and you have to know your friends pretty well.
One of the best parts of this place is that May is INCREDIBLY thorough with her directions and information. There's a massive binder of helpful information once you check in, so definitely check that out! Also, the washer is excellent, because it's a washer-dryer combination. It's literally three buttons to get it started, but be aware that it may take around 3 hours to finish, so just do your laundry in the morning and come back to clean, dry clothes.