For now I am staying with DL for paid tickets, basically to milk DL of all the benefits. But my travel is slowing down and I will probably only get GM status this year. I will probably do a status match to another airline before end of the year.

Right now all my credit card miles are going to AA, AS and AmEx (which will probably end up with CO). I am already flying other airlines more - used F9 last month and am using AS to Alaska this June. Fortunately you can fly to a lot of different cities non-stop from MSP without using DL. *A is especially attractive - ORD, DEN, IAH, CLT, PHL, EWR, PHX, and probably other cities are all available with *A non stop from MSP.