I've stayed there a few times in the last 12 months. I usually stay in the largest non-prestige suite (i.e., I don't do the presidential).

1) It's been OK. Service hiccups abound with certain room service things taking a lot longer to come than would be expected, or not coming at all.
2) Rooms show a bit of wear. Floors and walls are dinged up.
3) Ventliation/heating was super loud. Woke me up a few times at night.
4) Natural lighting can be bad depending on what side your room is facing. My first time was a corner suite so I had excellent lighting. My second time was a regular suite and the lighting was terrible.

I'm not sure I'll stay again when I go to Chicago. But then again not sure where I will stay.