Very good albeit pricey
Had a two-night stay here for an airport meeting. The sponsoring company got me a special corporate rate; I saw on the Hilton website the available general rates were quite high. As a Hilton Diamond I was placed on the 10th "Preferred" floor. A moderately sized room, nothing special, but absolutely quiet and nice blackout curtains. Nice view of the runway. No Executive Lounge.
The "extras" here are pricey, probably not surprising as this is the only hotel at O'Hare. Mini-bar candy bars at 4-5 bucks, Minibar and downstairs bar drinks 12-20 bucks, and so on. On the other hand, my $20 double Manhattan was quite well made. The "Gaslight Club" and restaurant are quite quirky, dark and evoking a Playboy Club feeling, definitely Chicago-ish for me. The buffet breakfast ($23) had decent standard choices and good fast service, though it's a long way from options at European or Asian Hiltons (I miss the smoked salmon).
The location is awesome, right in the middle of the airport, a 3-minute stroll to Terminal 3, for example. For gambling addicts like me, a $12 cab ride or (if you lose) a $3 El ride can get you to the Rivers Casino in nearby Rosemont, where there are also many restaurants.
On a business account, no question this place is worth it. There's no better place for an ORD overnight layover, as well. I were spending my own money I'd make sure I have a manageable rate and watch the prices carefully before eating/drinking at the property.