I would say that the experience varies greatly depending on the terminal you face but at least in general security wait times have dramatically improved over the past few years. United and American each have their own terminals more or less that can look somewhat grim but have a fair amount of services available. The United terminal has a tunnel that you must walk through to get to most gates (C Concourse) but at least they more or less synched together the audio warnings about reaching the end of the moving walkway. Walk to gates for American can reach 10-15 minutes if your luck is bad. Terminal 3 feels Soviet in design aesthetic but at least is being updated. Access to/from city center can be truly problematic - most hours of the day the drive (20 minutes no traffic) is at least an hour and without a car you are consigned to either an extremely overpriced (US$50) cab or an uncomfortable train ride. Delays are probably the worst aspect - part of a political game to make the traveller suffer so that Daley can get the airport expansion approved.