What worked amazingly well for me last year was to book early and await the free reroutes that came with schedule changes. A stop in MKE can usually be added to MSP-DTW in this situation with a minimum of additonal travel time. Routes scheduled for DC9 service are best, this are mostly being replaced by CR9s, that change of carrier is your invitation to reroute.

This year I have been doing end on end ticketing, mostly trying to turn great prices into useful trips. At this point I am booked up to 25 segments and 19k miles so I don't know if requal will be miles or segments, luckily it is stil early in the year so I'll get there somehow.

zooy, $33 per may be a little low for DL. UA will let you bounce around the system but DL has learned Midwestern geography and closed some great loopholes.