Nice hotel- awesome location, but a few flaws
I was here for a meeting, and really liked some things.
Location-
The location is awesome. I've been here before and taken the public transit from Midway Airport, and it was simple. This time, I took a cab and had a great drive along the Lake and saw the city at its best. From the hotel, you can walk the magnificent mile, access the lake, go to Navy Pier, and walk to a boatload of amazing restaurants. 
Rooms
The rooms were very cool. They are very modern, but still have some charm. No major complaints- I got a great night's sleep. 
Common areas
The layout is awkward. There are two main towers of room, and it can get a little confusing negotiating the conference areas and rooms. The fitness center is technically in the building, but it is underground and through several common areas. Therefore, after your workout, you have to walk through throngs of other guests. At a conference or business meeting, I really don't want to be seen not dressed for business. 
Service
This is my second Hyatt review where I have to knock the service- I hope it isn't a trend. At check in, I got some attitude from the desk guy. It turns out that I asked for an upgrade and you needed to be Exec Platinum to get it (I'm just normal Platinum). He pretty much made me feel like a bum off the street who asked for the presidential suite. 
Overall, this is a dated but OK hotel. If you get the right rate, it can be a great place to stay when visiting Chicago.