Not up to Hyatt's usual standard
We were at the same event as a number of other recent reviewers. I find it interesting that our experiences varied so much. For example, one reviewer says how the staff made sure the public bathrooms never ran out of towels. I found several that had and even more which had run out of soap especially toward the end of the convention. Another reviewer said how there was lots of hotel staff catering to every need. I hardly encountered any hotel staff other than the breakfast wait staff and had to seek them out when I needed something.
I didn't like the hotel for a number of reasons. It seemed like it had seen better days. First of all, having reception on the second level and splitting everything between two towers was inconvenient. The pools of water in the lobby were dirty and unattractive and only served to reduce the amount of space available to sit and chat with friends or have a coffee. I always worry about legionnaire's disease whenever I see stagnant water in hotels. Secondly, there was no proper coffee bar only the kiosk in the lobby. The function space area could have done with several of these kiosks but the lobby would greatly benefit from a full coffee bar offering a range of cakes, sandwiches and salads as well as somewhere to sit. There was nowhere to grab a snack apart from the kiosk. Thirdly, for a hotel of this size there should have been more restaurants and perhaps an ice cream parlour or pizzeria. When we arrived the steak house was open and we did eat there once. It was very good if a bit expensive. However, this restaurant closed for refurbishment on the Tuesday so during the convention the only places to eat were the bistro and the so-called Irish bar. These had difficulty coping with the volume of people attending the convention. Because the hotel is in the business district there were few alternatives nearby, Houlihan's being the only viable alternative if you didn't want to spend too long away from the convention. We found the service in Daddyo's to be very good and the food was good - they served proper chips with the fish and chips and the flatbreads were excellent.
The hotel also lacked bars. When we arrived on the Sunday afternoon neither the Big Bar nor Daddyo's were open. There was nowhere to get a drink, alcoholic or otherwise. We were amazed that such a large hotel wouldn't have a bar that is open all day. We quickly found Houlihan's next door but felt we shouldn't have had to go outside our hotel just to get a nice cold beer after spending all day travelling.
The hotel has no swimming pool which seems unusual for a property of this size. We learned from friends that the Sheraton across the river had a hot tub. This would have been very welcome after a long day's sightseeing.
Our room was rather small for a US hotel but we did have a comfortable armchair - only the one though. The bed was reasonably comfortable but the hotel needs to invest in some linen that actually fits the bed. We had a kingsize bed and the sheets weren't wide enough to tuck under the mattress. There was adequate hanging space in the wardrobe but not enough drawers. The mini bar had been removed before our arrival - why I don't know - so we used the empty cupboard to store t-shirts etc. We'd have appreciated a couple more power sockets to avoid having to take turns to charge our various electronic devices. The lighting could have been better. There was no central ceiling light, only table lamps and bedside lights. The curtains did an excellent job of excluding sunlight which was good for when we wanted to sleep late.
I wasn't impressed with housekeeping. Our room was dirty and I know from talking to friends staying in the same hotel that their rooms were in a similar state. There was a strip of two or three inches at the edge of the carpet by the walls that clearly never gets vacuumed. The whole carpet looked grubby and could have done with being shampooed. 
The bathroom was poorly equipped. The tub was very shallow as well well as being too short to fully immerse oneself. The shower was of the fixed-to-the-wall type. There was no wall shelf for toiletries although there was space on the shelf beneath the basin next to the bath towels for both our washbags. On the first day we had four face cloths, two hand towels and three bath towels. On subsequent days the face cloths reduced to two and then none. The hand towels were small. I'd have liked more of them. There were no bath robes. Shampoo, soap etc was replaced as we used the supplies provided.
We used the laundry service one day. This was very efficient and my linen trousers came back nicely pressed. The service wasn't cheap but it wasn't as expensive as some city centre hotels.
The buffet breakfast in Bar 151, priced at $22, was quite good - lots of options including fresh fruit, yogurts, cereals, various breads and pastries, cheese, cold meat, pancakes, bacon (only streaky), sausage, fried potatoes, scrambled eggs, other eggs cooked to order and juice. I ordered from the a la carte breakfast menu one day. That was a big mistake. My order took twenty minutes to arrive and was then inedible - greasy corned beef hash with uncooked potato. The breakfast in Houlihan's was better and cheaper (under $10) although there was less variety. The wait staff were very good, regularly topping up coffee and checking whether you needed anything else.
When we came to check out our bill contained a spurious item of $39 e-Standby Gue for each day of our stay. The staff seemed unable or unwilling to explain what this meant but eventually decided it was a mistake. I was glad I hadn't chosen the option of checking out online. Be warned, the hotel charges the room cost for your entire stay to your credit card the day you check in and each day's restaurant charges as you go along rather than when you check out.
I wouldn't choose to stay in this hotel if I were visiting Chicago other than for an event in the hotel's convention facility. Indeed, I'm not sure I'd stay there if I did attend another convention. I would consider the Sheraton or the Swissotel nearby. 
Internet access normally costs an exorbitant $12 per day but we avoided this by registering as Hyatt Gold Passport members on arrival.