I ended up going with the NMA-North River zone as thereuare suggested. I was offered $154/night for the Millenium Park Loop zone, but rejected it. My successful bid was $126/night (with $10/night in rewards - so this bid is equivalent to $136 according to Priceline) and I won the Mile North Hotel (formerly Affinia). Using the rewards was a bit frustrating, as I got a lot of errors that required me to restart my browser several times. However, I got a few free rebids out of it, so it wasn't all bad ;) Overall, very happy with my win - it's about a 40% discount, which I think is great for a summer stay downtown in a 4*. (I'll start a new post that details the win including the change of zone.) Thanks everyone for your help - I could not have won such a deal without you! :)