Worst Experience Ever - BETTER LESS EXPENSIVE HOTELS EVERYWHERE IN CHICAGO
Our stay at the Knickerbocker was by far less than average. The management behind your front desk was appalling. We had an additional $40 added to 2 different rooms each night we stayed totaling $240 total. We were told these were extra person charges, of which we were never told about in advance. We were also told this was due to the fact we had 4 people in our rooms. (Rooms had 2 double beds.) However, we actually did not have 4 people in our rooms as a couple could not make our trip, so we actually had 3 in each room. 
I was told by the manager (Wish I knew her name, shorter, foreign, hateful.) that she had house keeping check, and we had 4 people. I asked, did you count our backpacks? When did you have them check, as we had DO NOT DISTURB signs up the entire weekend. The whole time I was trying to resolve this, there were multiple people in line for the same thing, and other reasons, such as your hotel changing their room rate due to being sold out. Makes no sense.
Bottom line is, we booked the room at one rate through a coupon yes, but your coupon did not say there would be additional charges for multiple people in the room at time of purchase. It is illegal for your company to up a rate, after advertising it at a lower rate. Your "manager" was the most rude and hateful person I have ever met. Told me, "I don't have time to deal w/ you, go away." But eventually credited our room back as I would not leave until she did. I have never had such an unpleasant stay ANYWHERE in my life, and will never stay at a Millennium hotel again. I strongly encourage you to get rid of your front desk manager as she has NO public relation or customer service skills what so ever. Our entire group was completely disappointed w/ your terrible hotel and management that we will never be back. We should have known, because even booking our rooms using the Groupon was the biggest pain in the butt we have ever faced. No one on your staff was aware of the Groupon, nor did they have the brains to help us book the rooms w/ the coupon. We were also denied the use of our Groupon, until I called back and argued just to use it. Seems like you were trying to recoup your money from the Groupon by screwing your customers over at checkout. I have provided this to TripAdvisor as well, not sure how much good it will do. I still strongly encourage you to get rid of the half [--] "Manager" you have working for you. Never have I experienced such horrible service in my life, and this is someone who makes a living in the service industry??? Best of luck.