I was one of the lucky customers who snagged MM when CO and UA merged and they counted all the CO lifetime miles that included bonus miles (unlike UA, who only counts actual flight miles).

IMHO, MM is very valuable for E+ prebook, Group 1 boarding, free baggage, and *A lounge access. Especially when I retire in the future and will want to travel but won't have the ability to maintain high status from biz travel.