On the other hand, it seems like UA flights between MSP and DEN are now all on RJs, even one of those damn EMB-145s from time to time

It is nice to see an upgrade like that, though I remember when I worked for NW in 2008 in MSP, there was a pretty wide variety of planes on that route. I could swear I brought a UM to a DLH flight operated on a DC9!