I have lived in Chicago for 15 years and in all this time I've gone through several stages of tender feelings of belonging and rejection.
The city welcomes everyone but the alienation characteristic to big cities is an obstacle one must meet head-on. People may be friendlier than in other cities but they may be also more reserved than in smaller cities or towns in this part of the US. If you've heard of the welcoming Mid-western mentality and are looking forward to experiencing it here, be warned: this city will serve you a hot and a cold one, both in the course of one day. The diversity is a factor and as a long-term visitor, you should be flexible to adjust to different types of mentalities and behaviors so you can navigate social events successfully. Urban standards of socialization apply, just like everywhere else, but I have not encountered something like the 'New York spirit' or behavior. It is not standardized here so you have to stay flexible to enjoy the full cultural and social wealth this city offers.
You've seen and read promotional materials. Yes, the Magnificent Mile is there, with its stores, the restaurants are world-class and the diverse museums can please even the most pretentious of visitors. Go on an architectural boat tour, visit Navy Pier, enjoy the gardens of Lincoln Park and the vitality of Pilsen, but above all, connect with the people.
Take the city in, but not as an observer, but as a person who is scouting for a neighborhood to live in. Even if you're not planning to live here and are only a tourist for the week. Go on Meetup.com and check out the events Chicagoans attend. There are so many fun things to do. Do some research ahead of time and attend a street festival. If you have connections here, let them know you'll be in town. Because at the end of the day, you can always buy a postcard or take endless pictures of buildings and places, but they don't stay with you. What stays with you is how you felt, the good conversation over a meal you shared with some acquaintances you were too lazy to turn into friends, the laughter over an oversized dessert, the novelty of spending half an hour talking to various people taking pictures by the Bean or the confusing emotions you may have at seeing a racoon, a skunk, and possibly a coyote in the middle of an urban sprawl like this. If you get over the traffic and expensive meters, some angry people here and there, the cold temperatures in winter, the corrupt bureaucracy and the huge tax on all products and services you buy here, you may just have one of the best experiences of your life.
Chicago offers more than postcard experiences. It offers human and life experiences and it is for those that we really travel. Make it your home for a week or a month and you will make lasting memories. Make it your home for longer and you may never want for another.