I've been DM since March 23 (ends Aug 31, acquired through an Amex promotion) and have had two round trips: AUS-ATL and DEN-LGA. I'm 100% for upgrades. I have DEN-BOS coming up next week and my upgrade has already cleared. We'll see what happens BOS-MSP-DEN on the way home. DL isn't my primary program but they're a preferred airline for my employer and for these trips they were the best least cost option (lowest non-basic economy fare). I don't have the DL Amex... just getting upgraded on status alone.

If you have a chance to earn DM and keep it and your flight schedules avoid peak "consultant travel times" I think you could expect a reasonably high domestic upgrade rate.