Winters really aren't that bad (except this one, worst in something like 30 years), and I've found that my friends that moved here from warmer climates managed to adjust relatively quickly, and even began to appreciate the winter.
Chicago is probably the greenest big city you'll find in the US. The park system is magnificent, and not just Millenium/Grant Parks (though those are the most attractive ones). The public transportation is definitely convenient, though the L needs some serious work and is going through a bit of a budget crisis (mostly because our governor is a lunatic). That being said, it still runs, and gets you where you need to go on time (usually).
I also totally agree with the getting out of Lincoln Park/Wrigleyville area and exploring. Don't get me wrong, I love my nights out there, but there are a ton of cool, unique neighborhoods that are worth checking out.
Chicago really is an incredible, breathtaking city - and the new Calatrava "Spire" going up is going to increase that wow-factor by a lot. If you take a boat cruise out on Lake Michigan at night in the summer, there are few more beautiful city views.
And for pizza, Lou Malnati's edges out Gino's by a hair, and Uno is crap.