If you're lucky enough to get into Chicago, work your butt off and get yourself a PB because this is the course for it. It's very flat and fast with lots of aid stations along the way. After reading the rules, it stated that hydration packs and backpacks weren't allowed. It's something to keep in mind if you're looking to bring your backpack or vest along. Although I did see some people wearing them in the start zone so security must've let them in. I'm not sure how strict they are with that but better safe than sorry. The streets are lined with spectators, it was pretty amazing. So much support from everyone.
The expo was pretty huge and we got lucky and got in without a lineup in sight. I saw photos from the Friday that showed crowds of people and really long lineups. I showed up shortly after the 5K ended on Saturday morning and there was nobody. I was directed to the counter I needed and grabbed all my stuff pretty quickly. There were lots of booths to look through. I couldn't stay long but there were lots of big name vendors there. The swag was ok. I wasn't a big fan of the colour of the shirt but the design was nice. The shirt is made by Nike so it's great for running. The medal logo matched the shirt, it's a nice one. You can also order an iTab so you can have your finish time engraved and added to the back.
The entire weekend was well-organized, as any world major should be. All our questions were answered by signs they put up, people working for them, their website, and the event programme. Definitely run this marathon at least once.