As others have said, Chicago has its own vibe. That said, I lived on the East Coast until college and have spent substantial amounts of time on the West Coast, and I usually make the following comparisons:

* People in Chicago are much more friendly than those in places like New York
* Chicago's a less pretentious city than either New York or LA
* Chicago has a lot in common (in terms of friendly people, culture and vibe) with Toronto
* Chicago's a lot cleaner than most big cities
* Chicago feels a lot safer than many big cities
* Chicago has a great arts, dining and sports scene
* Chicago is an amazingly picturesque city
* Like many major cities, Chicago is partially landlocked
* Chicago is much more accessible (generally, it takes much less time to drive the same distance in Chicago compared to NY, we have a better public transportation system than LA)
* Anecdotally, the cost of living/visiting Chicago is lower than cities like NY, LA & SF

In terms of things to do in and around Chicago, it sounds as if you already have a decent list of ideas. What are you interests? What have you particularly enjoyed doing in other cities you've visited or at home?

I'd recommend visiting sometime between mid-May and late September. Chicago is a fantastic outdoor city when the weather is nice.

* If you're a sports fan, you can take in a baseball game or two.
* If you're a music fan, you'll be able to enjoy some free/low-cost outdoor concerts at places like Millennium Park, Grant Park and our many street festivals.
* If you're gay, our Pride Parade is fantastic (&, I think, the largest parade in Chicago).
* If you're a water fan, there's a big assortment of beaches and you may also want to take a boat dinner cruise on Lake Michigan.
* If you're an architecture fan, you'll certainly want to take the architecture river cruise as well as some of the walking tours offered by the Chicago Architectural Foundation. You'll probably also want to visit some of the suburbs that are home to many Frank Lloyd Wright homes.
* If you're a shopper, check out Michigan Avenue, Oak Street and some of the smaller, more boutique-oriented retail areas, or head out to the suburbs for a visit to Woodfield Mall, Old Orchard, Oak Brook or the outlets in Aurora.
* If you want to see some charming areas outside of the city, consider renting a car and driving to Galena, Starved Rock, Saugatuck or New Buffalo.