HI pal,
Living in De Fenwick at the moment.
I'm staying at the 14/f and you don't hear much at all, perhaps the random car horn. My appt is a nice size, just make sure you look at the lay plan of the floor you're staying on as the room varies in size. I had a friend who stayed in one of the Penthouses and it worked out alot smaller than mine, but had a massive balcony- which you wont use that time of the year, cos it's humid and really hot!
You won't get the extras that most hotel/service appt offer, like a gym and pool. It is a bit dear for just a room, but the service is good and all inclusive. Tho I would recommend you check out a few more before you put your money down.