I just did a one night stay at the IC London and I give it a mixed review.
I booked a Mayfair room and before traveling to London I logged into the web and saw I had been upgraded to a 1bdrm Suite. I also saw that the hotel was completely sold out. Then I arrived around 5:30pm and was told by a seemingly junior front desk person that they had a nice Luxury suite upgrade for me. She swiped my credit card and then said the suite wasn't ready and would I like another room. I asked how long it would take and she picked up the phone to call someone, let it ring for a few times, hung up the phone and told me it wouldn't be ready til 8pm. She apparently thought I was an idiot. I thought she was an idiot and knew it wouldn't do any good to call her on her lie so I just said give me another room. Then she asked me for my credit card and I had to remind her that she had swiped it not 45 seconds ago. "Oh, um...yeah".
It turned out that the lesser room she gave me was a 1 bedroom suite. So I wonder what the Luxury Suite was? Anyhow, I think I was the first guest to stay in this suite. The safe box wasn't connected to the electricity, the internet didn't work, the mini bar had no food, nor glasses and the room was very stuffy. However the mini-bar did have a nice selection of alcohol and both regular and pink Pommery Champagne. ^ And they refilled it for me later that evening. ^^ I just had to drink the Champagne from the bathroom glasses.
Nice Elemis bathroom products. ^
I went down to the fitness center which does NOT have a changing room

and saw it looked very much like the new fitness center at the Sheraton CDG. Darn near identical, except this one is larger and has 5 treadmills rather than two. ^ Must be the same company who set it up.
I didn't see a spa anywhere and didn't have time to ask about it.
I had called several days in advance to the Concierge to arrange something for me and upon arrival they had no clue what I was talking about.
But at check out, I got a good agent who removed my mini-bar charges without me asking. I told her I was very impressed.