They must have done a really good job in Chicago.. I live in Dallas and they've told me the network vision is done here and Spark is active and it's not much better, I actually got a text message from Sprint 3 or 4 weeks ago telling me how excited they were to announce the network vision was completed in my area (With a link that took me to the Sprint site and you could click on towers in your area showing all these speed/network upgrades)... and I live in the heart of the DFW area.. There are spots that are pretty good but for the most part it's pretty bad.... My best friend has AT&T and he smokes me every day no matter where we are in both coverage and amazing speed.... but if I am not mistaken I think Dallas is the corporate headquarters of AT&T Wireless.....
My step-son-in-law works next to a 4G tower in Minneapolis, and says the speeds there are amazing. I've had 8 down 12 up (Yes, that is correct) on my old GNext at times on 4G, but durring the upgrade, 3G was really bad. I still have bad data rates at times in more populated areas ( live close to one of the larger malls in the area, data sucks there)
The N5 I haven't found the speeds quite as nice, but more folks have 4G now, and I rarely use it due to my affore mentioned lack of need. But Spark is not on the N5 at the moment anyway, so until the next system update, I wouldn't expect 4G to be that impressive.
The question should not be "Am I the fastest", it should probably be "Is it acceptable for my needs"?. Chances are the NV tower upgrades are done, but after that finished, they still did some backhaul upgrades in Chicago, and that should help the speeds a bit, as will enabling spark (which should also help with signal strength).
The best phone plan and carrier will be different for every person. I'm mostly happy with Sprint (doesn't hurt they've compensated me for issues when I have had them), the bill is right and should get better (I have 4-5 people who should be joining my Framily soon enough), and the Service is pretty good now, and I think should only get better.