Top of the line-minor shortcomings
The rooms are spacious, immaculate, and beautifully furnished. We had a one bedroom suite, which included a large living/dining room overlooking Lake Michigan and the city. The view was spectacular. The HD TVs, one in each room, worked well. Free WiFi in the rooms was appreciated and worked well. No need to upgrade to the faster WiFi for extra cost. The staff is friendly to a fault and helpful. 
My wife and I had a couples massage in the spa by two very skilled massage therapists. The swimming pool is quite large and never seemed crowded. The locker rooms are stocked with everything you might need, including shaving razors.
Being on the 41st floor, we could hear noise as the building moved in the wind. A note at bedside explained how the building is designed to move in the wind, and was accompanied by ear plugs which we never used. The bed itself was plush and comfortable, but I found the pillows much too soft and didn't sleep as well as I might have. 
The bathrooms (we had two in our suite) were small compared to the rest of the suite. They had plenty of plush towels, but no special features and were nothing out of the ordinary. 
One real complaint is that whenever the heat came on, it would do so with a very loud snap. It could actually startle, so we turned the heat way down at night and kept the fan blowing.
The prices at the Four Seasons are through the roof, but I suppose that should be expected at a hotel of this calibre. For example, the massage for two was about $400 before tip! The dining room, however seemed moderately priced for dinner, especially if you order from the price fixed menu. If you want a breakfast of bacon, eggs, toast, and hash browns, be prepared to pay $29. I must say, though, that the bacon was cooked to perfection and was absolutely delicious. The hash browns were also very good, and not the usual afterthought that they are on most plates. 
The hotel is located at the northen end of Michigan Ave, attached to an upscale shopping mall, and a block or two from Water Tower Place and the John Hancock building. It's near many good restaurants. The concierge helped us pick a restaurant walking distance from the hotel. 
Being from the Chicago area, I don't know if I would stay there again. You can get similar accommodations at a better price.