Have you noticed how the boost now has a 'morning map' and an 'evening map'?
Today I took a non-boost rider from Evanston to the loop. The trip was mostly within the boost area defined by the map (Touhy to River North), but the ride had no boost because it originated outside the boost area. Once I dropped the rider off, I found that I had to go north over the river to get back into the boost area, so I went offline, and headed north. It took me 20 minutes to go about 2 miles, and then I got a boost fare going back into the loop, a 1.6 mile ride which netted me $6.01 with the boost. Once again, I was outside of the boost area, so I went offline and headed north. The evening map extends south to Roosevelt, but only goes north to Wrigleyville, and also extends further west than the morning map. It is interesting to observe how Uber is refining their incentives to minimize payouts and maximize participation.