I visited Chicago last week and I was impressed with the 4G Wimax Coverage in the City.
I was connected to 4G at O'Hare airport, while traveling on the metro, Downtown Chicago , Millenium Park, even on the 103rd floor at the Willis Tower, Logan Square and others.
Speed was great and no Wimax disconnects on my phone. (Nexus S 4G)
After using 4G in California ( Orange County, LA, Inland Empire) and Las Vegas, I was dissapointed of the terrible coverage.
I thought wimax coverage was going to be spotty due to buildings blocking signals.
Wish we had that type of service here in California specially in the OC area