Perfect in every way
A friend and I were in Chicago for Lollapalooza a few weeks ago, and stayed at the Four Seasons from Thursday night to Tuesday morning. We loved every minute of our stay, from the thoughtful earplugs for wind noise (which was not a problem at all) to the amazing view of the lake. Of course, the staff is what made the experience even better. We had a late dinner and drinks at Allium twice. The food was amazing, and the waiters were attentive and charming. At one point my friend left her phone in a cab, and the good people of the Four Seasons pulled the security video to get the cab number, called multiple cab companies to see who the driver was, and contacted other hotels in the area when the person who found the phone said he was leaving it with his concierge. I can't imagine any other hotel that would go to such lengths for a lost phone!
I've done a fair amount of traveling in Chicago, and I can say that the Four Seasons is hands down my favorite hotel in the city. The customer service is great, the dining options are top notch, and the location is central to everything. There's even a mall on the lower floors of the building, so when a sudden storm hit, we didn't have to go outside to find a store that sold boots. 
I'm looking forward to my next trip to the windy city, just so I can stay at this hotel again.