Great property but not my favorite location.
Selected JW Marriott to try something different in Chicago, where we go often for weekend getaways. The property gives a very nice first impression: friendly valet, sparkling clean lobby, even a lovely lilly scent. Check in was smooth and speedy. 
We were in room 1108 and were a bit concerned about noise because it was the first room next to the elevator bank. Fortunately we did not have any problems and could not hear the elevators at all. Our view was of an interior building scape, so we did not experience any of the noise issues that others have reported on this site. 
Our room was lovely. Very clean, modern decor, well appointed. The bathroom had an enormous soaking tub and a great separate shower with adjustable shower head to customize your spray. Very comfortable bathrobes and plenty of fluffy white towels.
We had a 1 king room and it was a typical size for downtown Chicago- not too small. Just enough room for an additional easy chair and table. WIFI worked well and was free because we have Marriott Gold status. $14.95 per day if you have to pay for it. Turndown service was a nice surprise and the bed area had great light for reading with small reading lights if your bed partner was sleeping. 
I did not use the fitness center or spa, but walked through to check out the swimming pool. I'm not a gym person but this place was impressive. Possibly the nicest I've seen in my travels. The pool was a bit of a disappointment only because it was part of the fitness area versus on a rooftop or exterior area. I felt very confined. But that's just my personal preference- the place was clean, towels available and altogether very acceptable. 
Here is my very picky piece of feedback and is no reflection on the hotel. Sadly the location was not my favorite. This property is located in the financial area of the loop and as a result many eateries and shops within close proximity have hours catering to the 9-5 weekday business set. Granted, it is absolutely not far to walk to other places but we found this frustrating at times (particularly Sunday morning) when we wanted to grab a quick bite somewhere other than McDonalds or Dunkin Doughnuts. There are places there- Pret a Manger, Au Bon Pain, Corner Bakery- but all closed. Even one of the drug stores had odd hours. Just a point of consideration. 
Overall, great stay and if I had business in this area I would absolutely stay there again.